Now its time to really fuck him. Try to point your cock upward with each thrust, aiming for his prostate. Each thrust will send wave after wave of intense pleasure up and down his body. Set a good rhythm and keep it up.
Start working his cock, too. Lube him up and jerk him. Try to get him on the edge, then stop. Smack his cock, slow down your thrusts, tell him you don't want him to cum again. Start working him up, get him to the edge, and stop again. Repeat this until you don't feel like it anymore: 5 times or less if you want to let him off nicely, but I've seen drooling, mumbling messes survive 15 or 20 ;)