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Hi! This is a new build but suddenly it's also a finish repair. I tested Ken Parker's Epoxy + Tru-Oil approach on the fretboard of this ukulele before committing to the rest of the instrument. It's a single (very thin) coat of West System epoxy (using the clear hardener), then 3 coats (so far) of Tru Oil. It's well-cured, about three months.

The bad thing happened yesterday: attempting to dress a fret end, I was using thick double-sided masking tape (https://www.mcmaster.com/76405A14/) with its liner on one side as a fretboard shield to the side of the fret. I learned this from a Looth Group video and it's worked great for me... on lacquer! I've used it on dozens of other materials with zero residue left behind.

When I peeled the tape yesterday, however, it left a lot of white goo under the areas that experienced file burnishing. The attached photo is after I attempted to wipe it off with 50% isopropyl alcohol and a q-tip. I was scared to use other solvents but I suppose I'm heading there now.

HELP! How would you get rid of that residue with minimal damage to the fretboard finish?

FWIW I'm generally pleased with the finish but I'll try sanding to a higher grit before doing it to the rest of the instrument. (I rewatched his video and was surprised to hear he goes well over 1000gr?!) I want to have an open pore look but this is a bit too open for my liking. Maybe that'll help.