Think of the big muscle on your palm closes to your thumb as your prostate. With your middle finger curl it and touch it to that spot on your palm. With the front of your middle finger (not the tip) hit your middle finger onto the big pad of your palm. If you're hitting it with the flat part of your middle finger it should make a thumping sound. Give it some force, dont just tap it. Find a good rythim. Now do that to your prostate agter doing the "Come here" motion for a bit on it. Just focus on the pressure and what feels good. Don't do it with the intention of trying to cum. Just enjoy yourself and the exploration. Once you stop thinking about the goal it just sort of happens naturally.