It's well known that the most popular fantasy for a typical heterosexual male is a threesome with 2 girls
If that's true, then most likely the opposite is true for a crossdresser. I myself often fantasize that rather than my wife bringing home another girl, that she turns me into a girl and brings home a guy. And of course to top that dessert with a cherry, she also helps me along to show me the ropes.
"Ok honey, so you take the cock in your hand like this, and slowly stroke it a little first. When he gets hard, then you can start sucking him"
"Sucking him? woah, that thing is so big!"
"See how good that hard cock feels?"
"Oh my god, this feels so odd holding onto a cock that isn't mine!"
"Now that's he's hard, take his cock into your mouth and start bobbing up and down"
"Mmmph! Oh shit! the magic wore off, I turned back into a guy! This is sooo awkward"