One rule for you to keep to yourself for now. If at any stage he cums without you asking him too, he must lick up every drop of cum. As you know, he should tell you when he is getting close to orgasm. If he speaks up, and it’s not time for him to cum let go or pull his cock out. Hopefully you’ll get enough notice so that he doesn’t cum. If however it is too late, an he does cum, by doing this he will end up with a ruin orgasm. Cumming without the pleasure and without losing arousal. At this point, make he lick it all up as punishment. This can before from your hand, mouth from your body, but much better if this from your pussy or even your arse. Use your imagination!
Run the two of you a nice hot bath. Tell him that you will be bathing together, but before he is allows into the bath with you, he needs to be perfectly trimmed/shaved to your liking. If you want to be very dominant, tell him you want him bald of public hair; that will certainly cause a little explaining when changing down the gym, which will be sure to cause a few blushes for him. Perhaps even ask him to shave his legs too if you like! All part of being a good sub! Anyway, get him to trim as much or as little as you like, and then join him in the bath.
During your bath, ask him to clean your body, every little bit of it. If you like, ask him for a massage, and feel free to get a bit more mischievous if you like. Over the course of this tease, you can cum as many times as you like, so if you want him to bring you to orgasm, go for it. After all, you are the dominant one here. As for him, wash his cock and arse thoroughly, but don’t let him even get close to the edge (of orgasm) at this stage. Maybe just sneak the tip of your finger into his tight arsehole, firstly to make sure he is clean, and secondly to get him worried about the evening ahead.