Answer:
Pee. When you urinate, stop yourself peeing a few times without using your hands. Use the muscles in your penis instead. Do it at least 4 0r 5 times each time you go. You will slowly be building up that muscle. After awhile, you'll be able to do the same maneuver while climaxing. It will stop close the floodgates so to speak. Extremely effective.The bonus(besides being able to control when you climax) is you'll become harder by doing this as well and sex is better afterword's because you gain some of the sensitivity that comes with climaxing without losing the erection.