When you grip while stretching, try to use most of the force distributed on the sides of your penis, since there is a nerve running down the dorsal (top) side. Also, you want to give enough strength into the grip so your penis does not slide out of your hand, but at the same time, too much force of squeezing can cause problems. So try to find that balance, with a bias of grip on the sides. I started off making an ‘OK’ grip using my thumb and index+middle fingers (3 fingers total) with most grip strength focussed on the sides of my penis, while the top part of my grip sort of rested and supported the dorsal area of my dick. Eventually, when my flaccid stretch gained, I upped it to index,middle, and ring fingers.