My hubby is about as straight as a javelin pole, and he loves it when I finger him during oral or other play. In fact, the strongest orgasms he has, and indeed, the one's he claims he cannot "slow down" or "hold back" on, are when I am doing oral, with one finger giving him direct prostate stimulation. I always keep one middle finger trimmed short just for him and for doing this with him! Holding my hand or looking at my hand reminds him daily, I am here to give him all the pleasure I can (he reciprocates more then his share, I should add). In fact, the anus is full of powerful, pleasurable nerve endings. You can finger him around the anus, or penetrate slowly with a finger, using lots and lots of thick lube, and if going for the prostate, simply aim your finger as if you were trying to rub his belly button from behind. It is kind of "up and forward". You will feel it like the size and indeed the surface texture of a walnut shell (but much softer, of course). Be mindful to have your nail VERY trimmed or at least smoothed, and do not scratch or poke the soft tissue with your nail at any point. That can do damage to the soft rectal tissue. It is all about gentle rubbing of the anus and rectum. If he enjoys this, he might enjoy small anal toys as well (Only get one's made for anal play, with a safe "flare" at the end, and always start small...with HIM calling the shots on when "enough is enough"). Tell them to relax and enjoy.

Indeed, indeed. It's just one more way to have fun.