When I masturbate and have plenty of time, this is one of my favorite techniques
Get extremely turned on then sit back and relax - this takes a while. There is a special spot underneath the underside of the head of your penis, following the raphe down. You should feel a tingle when you slightly graze it. For me, it is just about where my circumcision scar hits the raphe of my penis. (Picture attached) Use 1-2 fingers and slowly rub this point in a small circle or very slightly up and down. After a while I begin to pre-cum like crazy and I use that to lube the "spot". After a while you will have a tremendous urge to grab your penis and finish off, DON'T! This is the most important part. Resist the urge and continue with the circle. After a while you will begin to feel the tension build up, slowly, like warm fluid filling you from your toes up to your head, then a faucet slowly being turned on you will begin to cum. I don't usually shoot cum with this technique, but dribble. It's extremely erotic. Try using your other hand to stimulate your balls and nipples etc. I usually produce a large load when I accomplish this technique and a prolonged orgasm. Good luck!