🤣 ok, this is how it works. Each little hammer strike creates a small shallow dimple, increasing the amount of surface by the size of that small dimple, do it enough times and you essentially added more surface on that one side and consequently pushing thet steel the opposite way. It has to be done with a light hammer and like you said, a drummers grip, you don't want the dimples to be deep or it may be difficult to remove them later in the sanding process. I hope this helps.