My hands will be on her arse and s,lowly get closer and if I here no complaints ill keep going
With my wife, I can just stick it. Usually a thumb. Sometimes, she'll put a butt plug in before we start. Other women, I'll rub over it. The women I go after all have know I want their ass before the first piece of clothing is removed.
Gently tease and rub her asshole with my thumb, if it's something that she is into then stick a finger in her ass too. It just multiplies the naughtiness factor in the situation, so it really turns me on and is often enough to send me over the edge. I am bad with just leaving a pretty little asshole without any attention. ;)
drizzle a little oil /lube over it and ask if she likes the sensation, and would she like more touching teasing or exploring
I'm not a huge guy, but as someone who has had things stuck in my ass, I am considerate of the potential for both pain AND pleasure. Sometimes when I'm having sex with my wife (with whom I've never had anal sex), I rub her anus, and she seems to like it. I've also rimmed her while eating her pussy from behind, but not extensively. I have asked her to stimulate my prostate, but I could tell she thought it was weird, so I haven't pressed the issue. I wish she was more into it, though. One of my most intense orgasms was a blow job with anal beads. I sometimes stimulate my own anus with my finger or small objects (small vibes, large toothbrushes, hair brush handles), so I know how how nice it can be. My wife is a bit hung up on it though. At the very least, I wish I felt comfortable buying a proper prostate stimulator.