As someone who is working on the sinker, circle change combo, I'm having trouble keeping the movement just from the wrist, and not having the path of my elbow change. How can I prevent my elbow from rotating with my wrist? Or should it?
Can't say I've ever heard of someone trying to isolate the elbow from the wrist when throwing a pronated pitch. My suggestion is don't do that. Pronate the hand/wrist and let the elbow (and shoulder) follow.