My own, epoxy-resin itself needs priming - not for any adhesion problems, but simply to block the (yellow) light which it passes through. And my own personal preference for doing that is Tamiya Purple (TS-24), which may also be a lacquer-based paint - certainly something "hotter" than typical enamels - but that's only because it sprays extremely fine right out of the rattlecan: there is no problem with painting any enamels (AFAIK) directly onto my (Gougeon-type) Epoxy Resin. Likewise for Tamiya's Polycarbonate-application ("PS"-series) paints: except there's no way to get those back off, if desired - that won't also dissolve the Epoxy!
I had heard about 3D-Printed parts that you have to clean a bunch of waxy or powdery stuff from their tightest crevices, and then wash and/or soak them in solvent, afterwards - two more extra little Pains In The A** that modellers don't need - before painting. But I can't image the kind of plasticizers and/or crap oozing out of them which would prevent enamels from ever drying!
They have GOT to be able to do better than that - and we will LAMBASTE THEM WITHOUT MERCY , until they do...
Let me know when you got my eMail, David!