sculpted monstro, isaac and slimes

recently i finished sculpting monstro from tboi, i thought it would make for a good first blog. i don't have much experience with sculpting(or painting) like at all so it's not the best quality, but for my first ever "big" sculpture i'd say it's pretty good. isaac was made just before monstro. 

before this, i started making all the slimes from slime rancher. eventually i plan to make every slime, including every secret style slime and all slimes from the second game, but for now this is all i have. 

ONE PROBLEM. DOES ANYONE KNOW WHAT I SHOULD BE USING AS A SEALANT? the acrylic paint has been chipping off of my slimes, i do not want to same fate for my monstro. every time i find something that might work, i'm told it will interact badly with the polymer clay, it's hard to find what will work and i'm also a bit scared of ruining them.