I'm not sure if all gangbangs work like some one else mentioned, a bunch of naked dudes fluffing themselves waiting for their turn.
The gang bangs I've been in, it's one chick and one dude in the room at a time every one else is hanging out elsewhere, drinking, bulshitting, whatever almost as if nothing else is happening. Then when the dude is done, he comes out and in goes the next guy. Been in quite a few, never hookers or crack whores, just young horny girls and a bunch of young horny guys.
some call it amtrack but we call it the train