Gray card has always worked for me. Once you have your test print matching the gray, then I'd zero the color meter on the baseboard to the gray card for that pack of paper. I try to expose a gray card at the beginning of each roll. Then zero the color meter to the new gray card negative at the beginning of each roll with the color wheels on the head.
I'm not sure how one would use those other things. Perhaps you'd be out in the scene with the thing over the lens and shoot a frame pointing back toward where you'd stand to make the picture. Then try to match that negative to a gray card or something???