On manyvids typically the member orders the custom and you don't get the option to accept or decline. You just send messages back and forth and either upload to accept it, or deny it. Some members even when messaged after ordering can be very vague about what they want.
OP you could get a lot of visual info from scrolling the clips4sale humiliation section! When I do clips that revolve around an item if clothing, like jeans in this instance, I like to make fun of him for liking them so much, call him sweetie and say things like " aww look how much I have you drooling at my perfect butt in these tight jeans!" Try to squat over the camera like you are "sitting" on his face and say things like "You love being smothered by these sexy jeans don't you, my little pervert!" "Don't stop licking them, these jeans better be soaking wet from your spit, phillip!"
Of course, use your own personality! I often Google "humiliation scripts" and there is a ton of great info to riff off of there as well as erotic story sites like literotica.com
I'm sure anything you do with his name, your jeans, and your voice and awesome body will have him really excited!