When I first heard about WH's control, I immediately thought about how it would be possible, and there was only one thing that I could think of. And that is the fact that the brachial artery (which eventually provides the blood through the artery you feel in your wrist when you check your "wrist pulse" or radial pulse) lies very superficial (close to the surface) on the side of your arm closer to your body. So, I thought that the idea was to apply pressure against this artery, by firmly pressing your arm against your body. I played around with this, and found that indeed my heart rate did slow down, and eventually come down to a level that I couldn't feel. The benefit is that medically certified individuals can find the real radial pulse, and feel it slow down, and after being told by someone that already felt it how it is going to feel, it can be enough for a strong reaction.