Lace your fingers together around his penis with both hands towards the top of his shaft, and place the pads of your thumbs against that magic spot (the frenum) at the cleft on the underside of his cockhead. Rub your thumbs in slow circles around this spot for at least one minute.
Say: “Does that feel good, baby? I know this part of your cock is sooo sensitive. If I kept this up long enough, I could probably make you cum. But don’t worry. I’ll be careful to stop before that happens.”