I had to do some research on paper manufacturing a while back. In my part of the US, ordinary paper (writing paper, newsprint, etc.) is made in huge plants. I was surprised to learn that a lot of specialty paper (absorbent wipes, toweling, special surfaces, etc.) is made in very small facilities. The paper making machines are of unique design, specific to the the kind of paper being made, and specific to the actual building that houses them. While these papers are not coated, they do sometimes involve a rather complicated bonding of layers.
It would seem that a photographic coating operating could be similarly built - complicated and exacting, but not extremely difficult.