Years back someone borrowed my (hand-built) bass, wore a belt buckle and damaged the finish on the back. He felt bad. So did I actually.

It was originally sprayed with clear two pack estapol. I don't have the equipment to spray that - a professional guy did it for me for nothing, but he's now in Vietnam building houses or something.

I've since shifted to using spray cans of nitrocellulose lacquer when I build something.
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The damage happened years ago. I can see by the photo in the middle of the damage I had an experimental go at repair - I suspect with superglue - and buffed it. Not bad if it was! But you can see the lighter patches of damaged finish around it.

So... advice needed here:
1. Presume I need to sand the scratches back either:a) Until it's perfectly flat, OR
b) Go all the way back to timber on damaged section.
2. a) I then can spray nitrocellulose lacquer and it will bind beautifully with the two pack estapol finish, and everything is simple and wonderful.
ORb) Nitrocellulose lacquer won't bind to the estapol very well, so I can't use it. Even if I go all the way back to timber, there will be sections where it joins...
c) Brush on two pack estapol?
d) Something else?