A good way to practice technique is to get a 2.5 lb. coffee can and fill it with sand. Find a long countertop and put the can on the edge and practice. Soon you’ll be looking for a longer counter or more weight in the can. You can also have someone hold a phone book in front of them with their elbows braced against their torso standing in the on-guard position. I wouldn’t try this technique on a heavy bag; you’d be surprised at the power generated. I’ve seen many a sprained wrist.