u can only isolate the 2 muscle parts if u train them all the time. But for beginnerst that doesnt matter. Just squeeze ur asshole (a good training for this by the way is when u not going to the toilet if u need to take a shit but to go against it by contraction of the PC muscle but be careful and dont overdo it).
now you should be able to know how the PC feels. The next step is to find ur BC thats quite easy to. just try to get ur cock bouncing during an erection. now try the same thing when flaccid (thats a bit more difficult because the feeling of it is not that much when in flaccid state but do the same like on erection this will result in a good blood flow and getting faster erect even if not that aroused at all. If u train ths a log u can even get a 80-85% erection when u are zero in the mood of having sex. sure that dont makes much sense but see it only as a part of your training and its a prove what bc muscle training will give u
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i use this whenever i cummed once and should getting some rest because of the hormones after an orgamn that are leading to make u sleepy and not in the mood for sex. just pump blood in it and put it back into the pussy by 70-80% of erection and beginn penetration again. a couple of minutes and u will get the same arousal like before having ur first orgasmn ^^ (and here comes the 2nd round ^^). u can call it a "mind tricking" method if u want. But beware that the side effect of this results in a faster exhausted cock (u should give him some rest at least a day after u did this a few times).
for becomming a better understanding of the regions of this muscle just watch the attachment
greetz