I decided to try "liquid rubber" last year and I am pleased with the result. A lot of work and time, though.
I spray painted using a high quality liquid rubber made for industrial use: Protex by BioLub Industries, made in Brazil. https://youtu.be/H9bMmClhXQc. But I also tested with "Plasti Dip". This Plasti Dip, or similar, you can easily find in US and the end result was satisfactory.
Before applying "Protex", I diluted with Xylol solvent, and tested on a piece of foam I had. Only after a few days with no damage, I painted a test 10cm x 10cm patch on the boat foam itself. I used a small brush for this test, but waited for a couple of months (Covid helped here!) As it has not damaged the foam at all, I made two new patches with 2 and 3 coats to compare. Two coats seamed about right to me.
The finish is not bright, and if the foam had imperfections before due to lack of linen, of course they will not completely disappear (see pic). But even in this case it protects the foam from further degradation and renders a much, much better look.
I also decided, for now, not to paint the areas where the original protection was not peeling off or cracked. But will do before it starts.
Hope it helps