I will bypass the polyvinyl alcohol issue I have no experience with Kuraray products. I used Mowiol 4-88 (or 8-88 I am not sure) %20 concentration. It works like gum arabic.
More was discussed in detail
http://altphotolist.org/lists/alt-photo-process-l/200708/msg00258.html
When it comes making prints on glass you sometimes need a subbing for gelatin to adhere well. Usually in dry plates no subbing is necessary as long as the glass is thoroughly cleaned.
For siderotype printing I find that subbing and coating with gelatin layer is the way to go.
I made a few successful attempts but I don't pursue printing on glass, may be except for carbon printing. I am satisfied with the method I have used so I haven't tried other alternatives.
One of the easiest subbing is albumen, as it is used in collodion glass negatives. One egg white in 1 lt distilled water mixed to a froth, filtered.
I use 1 gr egg white powder in 300ml of distilled water and 1 ml of %28 ammonia. Pour it on to the glass and coat it like coating a collodion plate. Leave it to dry.
Coat it with %5 gelatin add some hardeners (chrome or potassium alum) also add a few ml's of alcohol to remove bubbles.
I coat the glass as if I am preparing a carbon tissue, I use a leveled stand and pour enough to make a 0,2 - 0,3 mm thick layer.
Leave it to dry overnight, then coat it like you are brush coating paper. Let it dry, expose and process it.
B&S sells amino silane, I read that might be the simplest of solutions to treat glass surface so it adheres to gelatin and similar colloids.
One more method here, for collotype process. I am looking forward to try this method
https://www.phototypie.fr/wordpress/en/adhesive-coat/
I believe that is one though coat, it contains sodium silicate.