getting him to cum in his pants

first off read the title!!! if you don't like it then freaking leave before you comment something rude and stupid please!!!

for those that keep reading and are nice: sorry but I posted this in the live and sex area earlier cuz I can't find a good kink group. the only comments I got were "that's nasty" "wtf?!" "why the fuck would he wanna do that?!" etc. I'm honestly so done with rude comments and half the people on this app cuz of it.

anyways real thing:

idk why but I really really like the idea of my bf cumming in his pants. he's done it once but that's when I was sorta asking him too. i want to be good enough at teasing him and then doing something else where it doesn't involve him taking his pants/underwear off yet I want to make him cum in his pants without me bringing it up. got any tips/ideas?