Bradley Williams is a buttery smooth player. His upshots are beautiful. In this video, he shares his technique and some drills to help perfect it. He focuses on the Nova, but the instruction is applicable to whichever approach disc you are using.
Feldberg’s approach to “making a mirror” of the back of the swing and the front of the swing is interesting, and different than other instruction I’ve seen. Btw, it’s called a “putting clinic” and the second half of the video is putting. It’s also very interesting, as it covers Feldberg’s step-through putting style soon after he developed it.
There is some good instruction in this video, but I have it in here primarily for Feldberg’s explanation of the scomahawk.