All I can say is I didn't get my first ass play till I turned 30 cause I though real men didn't let nobody touch their hole. Man, was I wrong. Nothing turns me on more than getting my pole teased and sucked on while she (or sometimes he) is teasing my hole open, then gently tapping my prostate.
When a guy cums most the pleasure comes out of his prostate. It makes most of the juice you throw and it part of the pump that shoots the jet.
If you can't get over asking your lady to work your hole, play with it your self in the shower. It takes a lot of the fear away when you do it yourself for the first few times. You will find your prostate quick enough: gently massage it. Put your finger in about two knuckles in and point to your balls. It feels firm. You don't need to poke it. Just press and rub a little.
First time I did this I practically fell over from the pleasure. No Shit. I had not cum in days (rare for me) and I was not jerking off, just exploring. When I massaged my prostate, it was like having an orgasm but without the muscle contractions. A bunch of HUGE slugs of cum flowed out my dead soft tool. It was fucking wild.
After I did that a few (dozen) times, I finally got the nerve to suggest it to my GF. She was up for anything, and after we trimmed her nails we went for it. Because I had already been up my chute and knew the territory, I could tell her where the prostate was. It wasn't long before she figured out exactly how to edge me, tease me, and juice me.
Some suggestions: One, be sure her nails are SHORT. Two, have her use rubber gloves, its cleaner. Three if your worried about what she's gonna find up your chute, you can clean your back sides out real quick if you have one of those shower heads that comes off the wall on a hose. Press it against your hole and relax. The water will gently douche you. When you feel full, just walk over to the toilet and dump the water. Repeat if necessary. No more than three times. You will be squeaky clean up there. Even if the ass probe is a no go, maybe you she can just munch your hole - a real good plan B.
You gotta be relaxed and if it doesn't work, do something else and try this again. One last thing: It's a real turn on for her to feel your tool jet down her throat while she feels the prostate pump thru her fingertip. Something for her to look forward to.
Oh yeah: LOTS OF LUBE.