I can't really talk about edging, since I've never tried it. But I believe the most experienced guys in here will say it has great beneffits in Penis Enlargement.
As for the grip, it should be tighter than when your jacking off.
When you're masturbating, basically what you're doing is almost just rubbing your penis, so it is almost just a matter of friction. When you're jelqing, you want to avoid friction, so you should do it with some kind of lubricant. Also, the point of jelqing is to engorge your penis with as much blood as possible, without causing any damage to your blood vessels or any kind of pain or discomfort. To make sure you're doing this, pay close attention to your glans while you're jelqing. When you milk your penis forward, do you notice that your glans expands? If see it happening, then that's what you are aiming at. If you can't see it, because sometimes it's hard to notice it during the movement, then gently place your free hand around your glans (don't close it tightly, just feel it) and see if you can feel it expand while you jelq with the other hand. If you can feel you glans enlarging with the milking motion, you're doing it correctly.
Keep in mind that you want your hands to slide over your penis, not rub against it. And don't jelq past the basis of your glans.
So, you should find a grip that allows you to feel that expansion in your glans without causing any pain or discomfort. Some light bruises or spots might show up in your shaft as a result, but that just means that you either didn't warm up properly, or that you're squeezing too much. If that happens, ease up a bit, and it should go away in a couple of days.
I hope this was helpful.