Well, the prostate is on the side towards the front of the body. It's in about a finger lengtyh. And feels rather nice when stimulated nicely. Though it can also make you think you need too pee rather badly if "too" stimulated.

You don't. If you "let it happen" you'll ejaculate (without an orgasm, a very strange but pleasant sensation).

It's much better if the anal stimulation is combined with genital stimulation.

And I've gone into more detail than you'll probably put in, but I suspect it'll come in handy if you decided to get less vague. Background to let what you *do* write come out "correct".

Oh yeah, on oral sex, I assume you know about the problems with gag reflexes and with teeth?