You can seal you art or inlines with any clear acrylic sealer. You probably won’t get the professional, gloss finish that resin head gets though. Mike
I would NOT add Acrylic paint to Poly Resin! Ever! Don’t know about Epoxy. but I’m thinking; NOT! The colorants sold in a paint store might work because they are concentrated. I have used them both in Oil-based products and Acrylic based materials.
Years ago I painted houses with a guy who still mixed his own tints. He carried a wire basket like an old-school milkman with squeeze bottles of colorants.
My work has spotted me samples of universal (solvent free) colorants and they work the same as the ones I have gotten from fiberglass supply shops. I have used them with resins (poly or epoxy) and for tinting foaming polyurethane glue.
The standard warnings apply: always test new materials off to the side first and do not add so much colorant that it ‘plasticizes’ (weakens/modifies) the strength of the cured material.
Tinting foaming PU glue with acrylic craft or tube paint is also a bad idea in my experience. It goes off too fast in the cup and makes a mess.