You want to apparently fart on-demand by asking your friend to "pull your finger," but because he's Korean, he doesn't understand your request.
The Korean version of this classic and gassy classy move might be called the "push my thumb" trick. Make a "thumbs up" gesture, and ask your friend to push it. He will push down on your thumb like a detonator, at which point you will release your "dok-gas!" (독가스)