Tapping the Sweet Spot

I lie on my back and gently tap the underside of my cock with a long, flat object - pen, pencil, chopstick - just with a flick of the wrist, and just softly at first.  Aim right for the sweet spot below the head and just keep tapping repeatedly.  Gradually you will be able to increase the intensity and frequency, but you don't need to hit hard.  It takes some time, which is excruciatingly fun, but the build up is tremendous!