I think the idea of "grabbing" someone -- with the hand -- is rediculous. Anyone with know-how will get right out.

How can your thumb and forefinger be stronger than my shoulder pulling my arm back in? Or actually, turning my arm and pushing toward you attacking your own wrist. If you don't let go it breaks.

I think locking is the way to go, using the forearms and elbows. Hitting is the hands job. Asking it to lock onto a much stronger body part/joint-muscle system is sending him out to die.