Pumping_Iron, you may have read this already somewhere else, but in order to stretch uncut, you should pull the foreskin back, and then grip behind the head and pull. You might try a few different grips. One that I find works well for me is as follows:
1. With your left hand, pull back your foreskin
2. Turn your right hand so your palm is facing down, and your knuckles are facing your belly.
3. Grip your penis between your index and middle fingers, with the first parts of the fingers, before the first knuckle.
4. Let go with your left hand, and pull outwards.
You might want to squeeze the head with your other fingers before gripping, to reduce blood pressure in the head.
I find that this grip lets me get a good pull, without very much slipping. Make sure you are holding tight enough to be pulling the internal structures, and not just the skin.
Any other comments or advice from other more experienced PEers?