First don't get to hung up on ingredients look at what it becomes after the reaction which is polyester.
If you need the part to have adhesion or be structural or just stronger you could thicken epoxy resin with talc, chalk, glass micro balloons, silica, chopped glass fiber.

The sun is not nice to unfinished-unprotected polyesters or epoxides So you should consider the RF properties of what ever you will use to protect the part from UV.
The parts you bought are still made of the same type material so you still need to consider protecting them where you have machined away the outer layer.
Regarding the ingredients:
2,2'-OXYBIS[ETHANOL] is a reactant not a solvent (and not ethanol)
1,3-ISOBENZOFURANDIONE and 2,5-FURANDIONE are organic acid anhydrides.
Styrene monomer is styrene (AKA vinyl benzene or phenyl ethene).

The talc and chalk minerals are to thicken the mixture and make sanding shaping the hardened piece easier.

Most paints are insulative or at least non-conductive and should be fine.
The filler should be fine also.