Good discussion on Coach Huey about the Wrong-Arm technique here. I'm better with pictures and video than I am with words, so is here is my take on the Wrong-Arm technique. The Wrong-Arm technique vs. Power is pretty straightforward, and I will get to it later. The Wrong-Arm technique vs. Counter is not as straightforward and cause for some debate, so I will tackle it first.
The diagram below shows the Fox DE initially obeying his Block-Down-Step-Down rules vs. the OT. If he follows his hands, his technique will take him right into the pulling Guard. How he attacks the Guard is the key to stopping the Counter play. If he literally obeys his Wrong-Arm rule and attacks the inside shoulder of the pulling Guard with his outside shoulder, he will be pinned easily and the pulling Tackle will not miss a beat coming around for the LB. The defense has forced the ball to bounce outside, but nothing is being disrupted. It is important to remember that maximum disruption is the goal and purpose of Wrong-Arming.

