There's probably all of what you mentioned going on to a certain extent, although most industry people won't tell anyone. Rumor-wise there might be other places to score.
It's all secretive enough so that turning tricks on the side and using stripping and porno as advertisement vehicles isn't all over whore tweets to read about. Yet there was Monica Foster posting on Twitter, wanting to get picked up along with her location. She's beyond sanity, really cooky.
Tory Lane, owner of a black hole in her rectum, was honest enough to disassemble the squirting myth as just being a means to circumvent the legal ban of pissing in the US. It was on a show called Inside The Porn Actor's Studio one of Howard Stern's minions does.