For the horizontal twist technique, you can bring one hand to the front of the weapon while moving the other to its rear, turning the handgun toward the assailant and maintaining a good grip. Importantly, this must be one simultaneous movement, with your forearms crossing. This twisting motion will weaken or dislodge the assailant's grip on the handgun.
If this movement alone does not cause the assailant to release the handgun, you should create a strong base by lowering your center of gravity and widening your stance. Then quickly and forcefully pull the handgun away from the assailant toward the center of your abdomen, using the muscles in your back and biceps. This technique has the advantage of comprising just one simple movement, regardless of how or in what hand(s) the assailant is holding onto the weapon. While learning this technique, you can decide which hand feels more comfortable grabbing the front of the handgun and which hand feels more comfortable going to its rear.
Vertical Twist Technique
The vertical twist technique can be done in two different ways. If the assailant is holding the weapon in their right hand, you can grab the gun with your left hand while stepping off line to the left. Your left hand should then strongly hold the assailant's wrist and arm in place. With the right hand, rotate the gun backward, directly toward the assailant's wrist. The key to this movement is to rotate the gun in a tight circular motion, quickly and forcefully.
Conversely, if the assailant is holding the weapon in their left hand, you should grab the gun with your right hand while stepping off line to the right. Using your left hand, you should, again, rotate the gun backward, directly toward the assailant's wrist, in a tight circular motion.