Basically just spin the handle as you would if you were trimming, but hold the ass end of the case against the pocket reamer. Doesn't take much to remove the crimp and it beats doing it by hand.
I just sit down to watch some TV with two bowls. One empty and one full of cases that need the crimp removed. And my little crimp remover gizzie. Next thing I know, the empty bowl is full, the full bowl is empty, and I'm done.