So this question arises from pretty derpy circumstances but what's the best way to remove epoxy/glue in general from the insides of (open) bearings? Would just applying a healthy dose of acetone be good enough and not damage the bearings (in some strange fashion)? Would I need to relubricate the bearings, and if so, with what?
Short answer is replace the bearing.
Reasons, in order of importance, 1) safety, 2) likelihood of success (bearing turning out good as new) 3) cost, 4) time.
Let me say this first; I am not recommending you try to dissolve the epoxy out; I am specifically recommending you not try. This really is one of those, "kids, don't try this at home" things.
A little googling on "what dissolves epoxy?" will identify a number of organic solvents that to some extent will soften/dissolve various epoxys. What will work best will depend on the exact epoxyyou're dealing with. Of the organic solvents with some reported ability to dissolve epoxys, acetone is the least toxic. Still, breathing the fumes would not be good for you, and it is very flammable. Methylene chloride (active ingreedient in many paint strippers) is apparently more effective, but is a.....serious chemical requiring some careful safety procedures- known carcinogen, pretty low concentrations breathed in can have toxic effects, can be adsorbed through the skin (causing toxic effects). That means to try to use it, a real respirator, with organic vapor cartriges ($100-$150), nitrile gloves, adult supervision/parental approval. Bearing will have to come out, you'll need a sealed container to soak it in, with container and cap that it can't dissolve.
Problem is, even with multiple soaks, it is very unlikely you will be able to get it all out. Given the tolerances that any decent ball bearings run at, little bits, a film remaining will significantly degrade bearing performance; you will have spent many times the cost of a new bearing, and not have the performance of a new one.