Yes, a lot of builders use epoxy as a pore filler. You apply it with a squeegee, or a razor blade. It's a pain to sand and level though… To imitate the Fullerplast I prefer to use a phenolic or poly oil varnish. Epoxy has a lot of uses in luthiery, like HHG its main advantage is lack of cold creep, which makes it handy for gluing fretboard, especially on basses. On top of the fact that it doesn't introduce moisture in the joint and that unlike all other glues it has integrity (for structural epoxy), which can be useful for desperate repairs. That being said I rarely use it, sometimes for inlays as epoxy can be easily coloured with Transtint type dyes, unlike CA. For fretwork CA is way more practical, just wax the fretboard prior to fretting and the squeeze out will clean up easily.