Probably someone else has mentioned this somewhere, but I have found that when I masturbate by cupping my hand into a "C" and rubbing it along just the back and sides of my erection, I can significantly prolong the time until ultimate orgasm. For me, this stimulation from based to crown ridge produces a very frustrating slow building orgasm. I start to get a sensation of a deep desire to have some sort of stimulation to the underside of my straining erection, especially to the glans. However, because the cupped ridge created by your thumb and index finger only stimulates the top and side of the penis, the sensitive underside is left yearning for any sort of touch.
I have found that I had masturbate this way, reveling in the feeling of the slow building orgasm and the yearning for stimulation to the underside of my penis. Because you are not stimulating the most sensitive areas of the penis, you can control the edging and delay orgasm by simply slowing down the strokes.
I would love to see what it would be like to be tied down helplessly and to have just this mastubation technique used to see just how frustrating the results could be.
If anyone was willing to experiment on this with a restrained partner, I would be interested in hearing the results.