Personally, I think having a glass of water ready for me is a nice touch. Of course it all comes down to just how submissive you are. Having a glass of water is a nice non-submissive gesture. Just a recognition of me and a thank you. You could leave it in the room all ready for when I finish or you could bring it after. Perhaps a glass of wine so that your bull can relax while you are doing clean up. Also nice. One cuck used to pep talk me as I called it. He was all "fuck her good!" "God she loves your cock" etc. I wasn't a fan but maybe your bull would be. I made him go sit on the couch to be honest. Ultimately I think you could just ask him. Tell him you'd like to do something for him and ask him what he would like.