yeah, I can see how that would be an awkward chat... if you make it awkward.
Expressing your sexual desires with your fuck friends should be part of the package. We are not all Hellen Kellers feeling out way through sex. We are capable of communicating our wants and needs and if you are not you are doing it wrong.
So, you could frame it like "I know you are X but I really want to do !X" and grovel at his feet because his sexual interests trump yours. Or, you can frame it like a wild, crazy sexual adventure. "Last night I was thinking about how hot it would be to fuck you and I haven't been able to get it out of my mind all day. Oh, we would have so much fun. Let's do it?".
Make it about the awesome orgasms you will both have, rather than him doing you a favor.