Hey John,
I use the cupping method, you hold the pistol as you usually would, then cup the hand holding the gun with your other hand. Being right handed, I cup the right hand with the left hand, hold my right arm stiff, straight out and locked, cupping my right hand firmly, with my left elbow slightly bent. I bring my right cheek down and lock it into my shoulder. Then pull into the pistol with my left hand. Now you don't need that much pull, with bb guns, just enough to stabilize the pistol.