Using rapid breathing, concentrating on the anal/prostate sensation as it's being stimulated, and I never touch my penis (The second I touch it seems to distract from the anal stimulation.).
I also experience an anal orgasm, which is much like the sensations of an ejaculation, but without the jiz. I can have multiple anal orgasms when getting stimulated, just like females. Again, it's a hands off the penis thing.
When topping my partners I do my best to teach them these techniques, and some are successful. The only problem is I've turned a couple of well endowed tops into bottoms...and I wasn't through getting pounded by them.