Hmmm - I've been doing this stuff for 40+ years and don't know of anyone that does that. I understand it will fill, but it also "locks" the grain - so there's no wood for stains or finishes to penetrate; it's also a very poor surface for adhesion of following coats - too slick unless it's sanded aggressively. That may well be why you are getting streak - Tru Oil doesn't build much of a film, it's more of a penetrating stain with some hardening resin. There's no place for the Tru Oil to go because it can't penetrate epoxy. It also has absolutely nothing to "grab" - no mechanical adhesion (and it definitely has no chemical adhesion on epoxy). You may eventually get an even-looking "finish" but - assuming you tested the epoxy on something before applying it to your guitar - I suggest testing the adhesion on the test piece - put a few cross-hatch razor cuts through it at roughly 1/8" spacing, apply masking tape, and pull across it. If more than 10-20% pulls off it's not sticking well and you may have peeling problems under use. Did someone recommend doing it that way? I hope it works for you - I can't see any advantages & it seems like a very strange product combination.