ghost sharpie autograph - how to remove?

[rhyno]

so, the guitar is unplayed, new, but several years old, as was the sharpie signature on it. signature was removed by original owner w/ laquer thinner in a quick wipe but the ghost image of the signature is still there. perhaps he didn't use enough elbow grease w/ the laquer thinner (he deliberately did not on premise he didn't want to turn a gloss finish into satin)

finish is polyurethane.

suggestions? i was thinking of starting easy...putting it under a grow light to try to darken the finish (like tanning), or isopropyl alcohol / goof off. have seen some suggest buffing (with what)? or even wet sand w/ buffing (grit?).

any suggestions are welcome.
mahalo

rhyno

(why anyone would let someone autograph a nice new guitar is beyond me)