I would say that you could ask if he’s ever had a guy suck his cock. And when he says “no”, ask him if he would like you to show him how amazing it can be
My divorced neighbor has been coming over and talking to me a lot lately I think he knows I'm gay every time he comes over here he's got his dick half hard in his pants to show it to me. One time he came over with his shirt off and I could see his hairy chest and hairy armpits and I wanted to get on my knees and suck on his cock but I didn't know if he was willing or not. Lately he's been showing me more and more so I don't know what to do