Think of a role play scenario, ideally based on things you've talked about. Picture it in your head and dress that way. It doesn't have to be full on dominatrix, it could be a nurse or doctor, or it could even be a killer piece of lingerie that shows off all your best betters.๐
Use his cum as lube for your strapon dildo is a great way to humiliate him. Most likely he will be disgusted by the thought of cum in his ass but using it as lube will inevitably cause him to cum despite his objections which will confuse and embarrass him like he never imagined๐