This reminds me of the way I used to coat copper clad board for PCB manufacturing with photosensitive etch resist.

We had a machine which held the piece of board vertically and lowered it into a container of solution by means of a motor and a threaded rod. Once fully submerged, the motor was reversed and the board was slowly pulled out of the solution. It probably took about three minutes for a board similar to the size of plate shown here.

The result was a very thin even coating. I think this system would also work to coat glass plates. The disadvantage is that both sides of the plate would be coated but you could either clean it off afterwards or use a peelable release film on one side and peel it off after coating.