There are many ways to consider hand checking applications in Self Defense. There are precautionary checking , sliding checking, Position Checking, limb checking, body checking, La-la-la-la. I think what you are doing to the opponent at the time counts, if you have worked with a partner or other student's in class and hit them they all will give you different reactions. Therefore you must have different controling factors. The learning and synchronization of both hands working together in order to maximize checking helps. But, I guess, what I do is keep the opposite hand either high along side my head or covering my solar plexus/centerline it helps in not losing it in combat. Other's are as you enter you cover over, under, and inside, outside the Line of Entry. Just my 2 cent's