What 'does it' from any particular chick to the next is too varied to give one global answer. Orgasms are easy enough but a series of rolling multiples where afterwards they just quiver off to sleep .. you might get lucky and do that on a first try but generally you'd have to 'know' the chick and the reason for that is because they can all be very different.
- There's a way to (i hate to say 'force') clitoral orgasms to occur from oral. -- Usually if the guy does the right things, at the right times, speed, pressure, escalation, pause/restarts etc, according to the chick's sensitivity and relative level of excitement (all of this is already a mess of randomness and we're only talking about one chick) then eventually you can cause the conditions for the chick to have an orgasm.
F that. I mean, it's ok, but you don't have to put up with it. You can -make- it happen, quicker and without the guesswork.
With your lips parted slightly, use a small amount of suction to draw their clitoris onto your tongue .. barely, level with your teeth, but use your lips to keep the teeth (generally) out of direct contact. Then use the motion of your tongue towards and away from the clitoris to cause a moving/undulating suction force. It's 'like' you're licking the clit, but most of the time your tongue stays in the same relationship with the clitoris instead of licking across it. The change back and forth of your tongue causes pressure differences on the clit .. lower suction pressure when forwards, higher suction pressure when back, and you can pretty much pick your own cadence for this. Certainly going along much faster than than with conventional licking or sucking where you have to figure out the pace they prefer, and even that can keep changing. With this, if you're using some elementary common sense about escalation, you can ignore all of their randomness and set your own pace without having to constantly refigure what their deal is. I like to punctuate this process using counting sets with a harder 'one'. Do a set of four motions and the first one is harder than the others. do a set of six and the first one is harder than the others. Do several sets of ten in a row and the first one of each set is always harder than the others. A bit harder, don't go nuts. If you want them to really blow their head off when they orgasm, get them close to coming and then back them off a little before building back up again, you can do this several times but then you'd need to keep up with whether or not you're causing frustration instead of intensity.
I can essentially express the success rate of this as a percentage - it's worked on 99% of the chicks it's been used on, (not bad), with one 'flyer' (and I'm pretty sure it would've worked on her too if she could have dialed back her neuroticism/need for control and just let go) - including working like a charm on chicks who said "no don't bother, I can't get off that way."
As far as multiples from oral clitoral .. you're back to some per-chick randomness. After orgasm their sensitivity will skyrocket for a random amount of time and usually you'll have to back off your speed and pressure enough keep them plateaued without being either too much or too little until you can begin to go faster again. If a chick is highly sexual, aggressive, comfortable with her body, you might be able to skip the plateau phase and stay dug-in for rolling multiples .. but if you try that and she can't handle it then she's going to buck out of it and you'll have to restart or move on to some other position/activity. Epic either way. You'll be remembered. A bonus of this is that anyone can do it. My tongue is like I'm 'double tongue daddy', if some girl asks me if I can lick my nose I reply (they're standing at common distances) "I can pretty much lick your nose." And there's no downside to that, but for the above method, if someone can get their tongue between their own teeth and level with their own lips, they're good to go. So, .. everyone.
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You've probably seen the curled fingers manual manipulation of the g-spot by now. If not you can look it up or someone else is bound to post about it. It might be the closest you'll get to the megagasm you're wanting, and it is good for quick-succession rolling orgasms, but the chick has to be in-tune with her g-spot for it to work that well. She'll need to have a fit muscular uterus, either by freak chance which is rare, or from having some kegels experience, and have either natural (again, more rare) or learned enervation of her g-spot ... so it works well and she's linked up with the pleasure that it can put off. The number of girls that it will work well on seems to keep increasing, but you can get a clunker who is, presently at least, not super-geared for it.
Variations: It tends to be taught as a two finger process. That's great but for whatever reason, maybe it's my angle so that my mouth is up with the breasts and mouth, I find one finger (middle) to work better, and this can cause the index finger to be in the way, but also allows the ball of the index and middle finger a better contact angle to impact/rub the exterior clitoris, and allows the ring finger (if you want) to sneakily add pressure to the anus, or even to slip inside slowly and ride the same fingering motion .. sometimes simply duplicating the motion, sometimes also adding a grip pressure to the upper side putting sensation on it and also compression on the perineum. If the chick is not hopelessly uptight, they'll like this to say the least. But don't go nuts with it for a long time because they can be sore from it later and you don't want any after-event re-scoring of how much fun they remember having. It can be 'Wow!!', or it can be 'hmm that's kindof sore, i don't think I'd like that again'. Fine line. Be mindful.
Some math on the above, while the clitoris has some 8,000 active nerves, and the g-spot is the obverse side of the same clitoral node .. the highly popular vagina has far far far less to not even be in competition, but the anus has another 4,000 active nerves just sitting there doing nothing ... half as much as the clitoris .. but shockingly equal to the 4,000 active nerves of a guy's penis. Sensationwise, adding it in is a lot more intensity.
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One more bears mentioning, if I could remember the several things I've seen it named I'd look up a link .. but this is how it goes: If the dude's dick is long enough and the chick is skinny enough (and/or knows how to turn her hips forwards) the guy and gal can lay on their sides, face to face, with their legs closed and more or less straight. That's it. If you can get , and stay , inside her and bang away with everyone's legs closed and straight .. the pressure and sensation for the chick is mindbending. But the sizes and/or fitness have to help out. If you keep popping out it won't work.
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And one more. Chairwoman. The previous ones have been more of the guy being in control. This one relies on the chick to orgasm herself unconscious, so she'll need to be 'greedy'. Encourage her to cum as many times as she can 'cos you like seeing it', etc. Chairwoman. There's something else called Chairman, this isn't that. Think of Chairman as Reverse Cowgirl in a chair .. chick on top, facing away. That makes Chairwoman the equivalent of Regular Cowgirl in a chair .. chick on top, facing each other. Helps a lot if the chick is tall and/or long legs .. and/or for the chair to have no arms or, preferably, arms but short arms. The chick should be able to control her motion either from her feet reaching the floor (while also grinding your lap) or from thigh contact with the arms of the chair .. but not so that it's tiresome or painful. Used to have the Perfect chair for this. Miss it. Everything the chick can control about speeds and pressures and insertion angles with Cowgirl, she can do even better with Chairwoman. But again, you won't be in the position (so to speak) of doling out the orgasms this way, everyone will have fun but if she doesn't give herself ten, twenty, thirty, you can't really do anything more than encourage it .. or at best force more contact pressure and penetration depth during orgasms so they might trigger into multiples.
Enjoy. Interested to see what all turns up in this thread!