Well, 100 years ago, plates were once coated by hand in rooms of individual coaters in dark red safelight and heavy lab smocks. Then they began coating with a cascade coater with sheets of glass passing under on a felt plate. A special cutter then cut the huge sheets into individual glass plates. Many coaters were similar to that of Jim Browning.
Film was not an early contender, but when it was, it was coated using a trough coater as shown here on APUG in a video. Paper was coated the same way. Later coaters added a doctor blade or air knife to reduce ripples and irregularities.
Drying of plates was difficult, but drying of film and paper was rather simple given enough room. The coated material was hung in festoons from the ceiling of the coating room and allowed to dry. However, each loop in the festoon introduced a "kink" or coating defect which limited the longest length of good coating to just a little less than the distance from floor to ceiling.
Accuracy and precision were pretty good, all things considered.