So I thought, maybe I can mix something up?
Step 1: What to Use?
Next, I tried spraying some watered-down PVA glue. I used a High Volume Low Pressure (HLVP) sprayer (pic 2) to get a fine spray but you could probably get away with any type of sprayer. When it was wet, it looked like it was going to work, especially a heavy even coat. Unfortunately, when it dried, it was only a bit better (pic 3) than the brush-on PVA glass.
I figured out that the reason it wasn't obscuring is because the PVA dries glossy and not matte. I looked online and found that artists use something called Matte Medium (pic 4) to reduce the glossiness of paint, and after a trip to the art supply shop, I mixed up 1/3 MM to 2/3 water and sprayed glass number 3 (pic 5). This seemed to work perfectly so I mixed up more and started on the doors.
Step 2: Finished Door!
I didn't try, but I'm sure you could roll on the matte medium. If you try this, you should make a thicker mix than the sprayer mix. Also, you could mask off any clear glass you wanted to leave as well.
When it is fully dry, you can wipe it down with a wet cloth but I doubt it would stand up to strong cleaners.
If you are doing it with a rented property, it easily comes off the windows with a stanley knife blade and peels off once it is started (similar to PVA).
Enjoy your frosting!