Begin by self-stimulating regularly (3-5 times / week) to become accustomed to the level of sensitivity and stimulation:. Try stimulating the scrotum only for a while: maybe several weeks. Then, eventually, you should be able to stimulate with varying force and pressure until you decide to ejaculate.
You can also practice Kegels to attempt to delay; Kegels are useful when the ejaculation is near or beginning and work to stave the ejaculation off.
If you cannot self-stimulate without gaining control, use a condom to reduce sensitivity while self-stimulating. A lubricated condom is suggested to start, you don’t want to get chaffed.
Next: make use of the refractory period after ejaculation. How soon can you achieve an erection after ejaculation? How long can you stimulate the second erection before ejaculation? Experiment several times a week with multiple erections and ejaculations. Although results may vary: men lose / regain their erections at differing rates. Many men experience less sensitivity during the second erection.
Next: use more lubricant. Reducing the friction may help him last longer.
Next: How much foreplay are you engaging in. Try more or less, or different types of foreplay. Try more or less focus on the penis to control the level of stimulation. If you are achieving an 8.5 level of stimulation before attempting to penetrate, where a 9 is the point of ejaculatory inevitability, penetrate when you are a 6 or 7. Never carry a lit match into a dynamite factory.
Next: use a condom during intercourse: Use a thick brand condom: Trojan Enz will work if you can use latex. You can get lubricated or non-lubricated, your choice. You can also use a lubricant with your partner as well.