Before you go in for the gusto, tease the butt. You’re working your way around your partner's body everywhere else, reach around and let them know you’re interested. And don’t be surprised if they do the same to you. This lets each of you delicately test the waters and see how your partner responds. You might feel a tightening of their body, and you might want to tighten up the first time they try it on you.  But, loosen up.  Let it go. Once you feel how good a light rubbing of the sensitive butt can be, you’ll be more likely to let them take it further, and they’ll likely let you work your way all around their body too.