The hapkido hand shake defense is a way to escape from someone who tries to hurt you by squeezing your hand hard during a hand shake. It is also effective if someone refuses to let your hand go after a hand shake. The technique allows you to use the attacker's tight grip on your hand against him.
Squeeze the attacker's hand hard. Since he is already gripping your hand, it should be easy to hold on. Nevertheless, grab his hand tight so he won't let go.
Spin your body completely around to the left. This assumes that you are shaking hands with your right hand. As your body comes around, allow your right hand to move behind you. Your right wrist will naturally turn downward and inward until your thumb points toward the ground. This is quite comfortable for you but incredibly uncomfortable for the attacker since his wrist is turning downward but outward.
Sandwich the attacker's hand with both your hands. When you are completely turned with your back to the attacker, reach behind you with your left hand. Place it on top of the attacker's hand. At this point, the attacker will start letting go of your right hand because of the pain you caused by twisting his wrist. Sandwiching his hand prevents him from getting away.
Keep spinning around until you are facing the attacker again. Allow your left hand to move around the attacker's right hand until he is palm to palm. At that point grab the attacker's hand tight with your left hand. Pull your right hand away as your body comes around.
Sandwich the attacker's hand again. This time cover with your right hand. Clamp down tight with both hands. The attacker is now in an uncomfortable position with his wrist twisted, in extreme pain and no way to pull his hand out. Continue to twist the wrist and push the hand toward his body. This causes even more pain. The attacker will be up on his toes and at your mercy now.