Need some finishing advice

[beerbelly]

I'm working on refinishing a 2011 Epiphone SG Junior, and have come across a type of finish I haven't worked with before. I've removed "poly" finishes with a heat gun before, and I usually find a color topcoat over a Fullerplast-type sealer. This one appears to be the exact opposite- color coat directly on wood, with a satin sealer over that.
Heat or CitriStrip doesn't seem to budge it, and when sanded, it smells like Bondo, which is polyester, so I assume that's the finish.
In the past, I've used de-waxed shellac as a barrier coat between polyester and a new nitro finish; will that work here? Is there such a thing as a sprayable polyester finish?

 

[Joe Desperado]

If you can get shellac on it, no reason that wouldn’t work just fine.

 

[lowatter]

Run it through an overhead sander perhaps?

 

[beerbelly]

I've decided to take it down to bare wood with my DA sander. I'd rather know what I'm dealing with than guess which finish it is or what to topcoat it with.
Not fast, not fun, but weirdly rewarding when I get down to the wood. Looks like 5 pieces of basswood.

 

[beerbelly]

Whew!

 

[Joe Desperado]

Those bridge post holes look huge! What bridge was on this?

 

[beerbelly]

I drilled them out to plug them; the roller bridge I'll be using has narrower post spacing: