Sounds like you are doing pretty well as it is. A couple of things I can suggest is short term abstinence (a week or so). Abstinence makes the cock harder and the orgasm stronger! So does edging.
Yeah, I like to wait a couple days sometimes when family goes out of town and I have the house to myself. Then I generally like to spice things up by doing different little things, and watching some of my favorite porn. I also like to think about girls that I know that I'm like... in love with. The results are usually pretty surprising.
pot? one time i was really really... really high (to the point where i was literally "stoned") when i did the "ultimate hands-free" method, the orgasm was undescribably amazing. The feeling you get right before you cum stayed constant for like straight 30 minutes. During that time the feeling of the "pre-orgasm" was so strong that my whole body was having an orgasm. My fingers, toes, arms, legs, neck, back, butt, and my anus was having an orgasm literally. Especially my asshole orgasm so great that it actually felt like it was shooting out asscum. My while body was shaking in orgasm as if i was being electricuted. That went on for 30 minutes. When I finally came, it felt like an eagle flying over high mountains after high mountains and finally shooting straight in to the sun at the speed of light. I even pictured the orgasm I was having. It was the best of the best orgasm Ive ever had. It was too good and heavenly that i was crying and laughting at the same time after i came. I felt so happy that I was thanking god for creating mj for us lol. anyway... its something that everyone should experience. its just too good to know experience it. try it guys.
dude just jerk off until you're about to cum and then stop... then start and stop right before you cum again.. repeat until you can't stand it. you will cum hard, trust me.