This will all be a bit cryptic, but the point of these drills is for you to figure out how to get these feelings rather than telling you what specific movements to do. Trust me when I say it's a lot easier way to try to learn this stuff an not just everyone being cryptic for the sake of being cryptic.
LYang wrote:It's the recoil feeling that I don't understand. Either I have not felt what I am suppose to or I have felt it but didn't know it. I let gravity pull the disc down, and when I feel the weight I am suppose to snap the forearm (which causes the snap of wrist) and grip hard right?
The downward hammer pound is more like an overhand or sidearm throw. The point of doing it vertically is to have gravity do most of the work for you so you can get the feel right. If you first let it happen passively you can then figure out how to actively strengthen the pound. The recoil feeling you get happens because the disc is pivoting about the lock point rather than slipping out of the lock point. It's because the disc is rotating rather than falling in a straight line. If you have that feeling then you can switch to doing it horizontally so that you're initiating the hammer pound rather than gravity. Then you do it horizontally but "backwards" to get it for backhand. That's probably the most difficult part.
The idea is to experiment with what you have to do it get that feeling for each of those steps rather than trying to emulate some motion that someone else describes.