Your best operator knows things nobody wrote down. The setups, the tricks, the one thing that press does when it's cold. When he leaves, it leaves.
Have him write it down once, even as rough notes and a few photos from his phone. Email it to Stan. Stan turns it into a lesson and a test, in his words. He checks it. Now it's in your shop's library, and the next guy learns it on his phone.
You print the procedure, who's trained on it, and when. It stays after he goes.