What did you sub the acetate with?
Well, I went by some information on "The Light Farm" and based the subbing on the recipe on p 187 of Wall's 1929 book "Photographic Emulsions" (with acetone variation) but took some liberties to make a very small batch. Wall's recipe makes about a liter. It was roughly as follows:

2g Gelatine
20ml Actetic Acid (Vinegar 5% Acetic Acid + Water)
50ml Methyl Alcohol
50ml Equate REGULAR Nail Polish Remover (70% Acetone + additional Gelatin (and other additives))

Soak the gelatin in the vinegar and melt to 55 deg C. Add the alcohol warmed to same temperature while stirring. Add the Nail Polish Remover (aka Acetone) warmed to the same temperature while stirring. You need to use REGULAR style polish remover. The friendlier stuff does not contain acetone. I used equate (Walmart) but the MSDS for any brand I recognized was basically the same; about 70% acetone.

Tape your film to a piece of glass. Use a cotton ball to wipe down the film with the subbing mixture. Do not rub, just wipe over the film and then set it aside. When dry in a few minutes it will look a little streaky but the streakyness will disappear when gelatin/emulsion is applied - just as stated in Wall's book. If you gently touch the film with your finger you will notice that the non-subbed side will still feel like smooth acetate, but the subbed side will have a little tooth/roughness to it. The "emulsion" stuck right to it when applied and did not stick well at all to a piece of the base where there was no subbing.

Treat this as a starting point only! This was literally a garage project since the methyl alcohol is gas line antifreeze - which is just methyl alcohol anyway. It hasn't been tested at all other than I can tell you that I do not seem to be able to rub the "emulsion" off with my finger and it bends with the film base without flaking off or anything. I did not yet subject it to any liquid tests.

If anything, I would try to get some more acid into it. I did not have glacial acetic acid which is what the recipe calls out.

However, I think I will take this sample off of the glass and put it in some developer temperature water for 10 minutes to see what happens.

-- Jason