The only LF lesson I ever got was the care, cultivation, and operation of the 4x5 Grafmatic 6 shot magazine. I didn't have a clue how to work it so I made an appointment with an old photographer still operating out of his upstairs studio on the main street. He grabbed the Grafmatic, opened it, checked all six septums for straightness, reloaded it, and cycled through all six in under a minute. It was a wonderful blur of hands that took me a half hour of careful instruction to repeat...very slowly.