Brush lines when sealing EVA foam with PVA / Acrylic Emulsion
I’ve found that when sealing EVA foam with some sort of PVA glue or acrylic emulsion (in my case, Mod Podge), I get all kinds of brush lines that are absolutely horrible to try to sand out. In fact, they really don’t sand out at all, or I will accidentally sand off some foam underneath! This happens even when using a foam brush and makes the sealing process NOT A LOT OF FUN.
The PVA glue / acrylic emulsion is too thick. Due to the thickness, it can’t flatten out on the foam.
Mix the PVA glue / acrylic emulsion with water! The excellent post linked below of different mixtures recommends a 3:1 PVA to Water Mixture. I just add in some water with the Mod Podge so that it is still definitely Mod Podge and sticks like glue, but is much thinner and spreads out nice and flat! Apply several light coats of it on the foam to seal — usually about 3 coats in total. It’s easy to do as it dries very quickly!
As I mentioned before, definitely check out this post on the RPF: The (somewhat) definitive guide to sealing foam and keeping it flexible