Basically, the solvent has to evaporate out before the epoxy cures. The less that escapes before hardening, the more “rubbery” the epoxy will be. So longer cure time epoxy is better to thin than shorter. And faster evaporating solvent like acetone is better. Lacquer thinner works too. Long cure epoxy dries nicely with denatured alcohol added up to around 20% or so. I haven’t tried thinning any more. No reason too. Always try it out a test mix first to see if you end up with an acceptable cure.

Multiflyer