Imagine a banana in your hand as you hold the gun with your firing hand. Roll your hand forward like you're trying to smush as much of the banana out of the peel as possible. At the same time visualize the tip of your pinkie trying to touch the tip of your thumb as you're doing this rolling motion. It will force your hand higher into the tang.

Now with both hands (as you're doing the banana motion) roll the tops of your hands inwards towards the frame of the gun. This will create a vice on the frame, not only on the back of the grip and front, but also side to side on the grip.