OMG I KNOW! I can't believe I'm gonna admit this, but I have actually practiced on my dildo, for the express purpose of fic writing

let's see... do you know about Minotaur's sex tips for slash writers (http://www.squidge.org/~minotaur/classic/oral.html)? That's universally useful, though not so much with telling you what pre-come tastes like. *shudders*

and here is the fellatio tag (http://community.livejournal.com/writing_sex/tag/fellatio) at writing_sex.