A little begging goes a long way, if you're playing submissive. Asking him to please fuck you, to please fuck his girl, etc. will probably strike the right chord you're maybe looking for. It may feel strange at first, but keep tabs on those feelings, and see how different phrases resonate for you. Or try exercises where you're bound and blindfolded and teased and only get more of what you can specifically find the words to ask for. That can go on for quite some time until you become very blunt out of necessity.