This technique is amazing. Into the shower you go, grab a bottle of the cheapest conditioner you can buy (cheaper is usually thicker and better for lubrication I've found). While your penis is still limp, cover it, your balls and the insides of your thighs with the conditioner. Now bend over and place your still limp penis between your thighs. Move up and down letting your penis slide between your lubricated thighs. You might need your hand to keep your penis from popping out.
Try it a couple of times, once you get the technique down you can cum in seconds (perfect for the quicky while the wife is in the next room). Good luck!