There are people who organize these types of events, it's generally somewhere around 200$ per guy, some of that money goes home with the organizer and some of it with the girl
The vagina doesn't seal itself up during menstruation, so the mechanics are the same but maybe your question is more about having sex during menstruation in a way that would make a partner not even notice?
Been considering this question for way too long. My clients look very different than the people hitting on me at clubs/gas stations and my FWBs. The only real crossover is that an alarming number of them are in IT.
Honestly, I don't think I'm a good match for anyone who posts even semi regularly here (I'm fat, weird, and old ;)). I''m here to learn and pass the time, with the added bonus of perving out on pictures of pretty ladies.
I use the DoxyPEP protocol. So far so good. The studies available are mediocre at best but it's a hell of a lot better than nothing. I'm glad it's being offered now. :)