I'm not male. But I heard this way to masterbate from my ex-boyfriend. I told my [new] boyfriend about it. He tried it, and found it remarkable. He told his cousin about it. That's all his cousin does now.
Get some lotion, a plastic sandwich baggy, and a bed. Put as much lotion as you want inside the baggy on your penis. Place your penis in between a mattress and boxspring [with it inside the baggy] that is just your height when you're on your knees. Then, just start humping. Apparently, it's awesome. Have fun.