These old inlays are done with hide glue, and release easily. Modern inlay, including mine, is usually done with cyanoacrylate or epoxy, neither of which are easily released. Generally it's not considered a big deal either way because new pearl inlay can look just the same as old. In fact, here I was able to reuse only about half of the ones I removed. The others were already too thin.
I'll now proceed to level the fingerboard just as I would on a modern guitar, using my favorite sanding block, my old reliable Stanley plane body:
Egad! Even with the filling regluing of all those chips, even more are revealed or knocked loose in the first bit of sanding. I'll fill all these tiny ones before continuing my sanding:
After filling all the voids, I'm going to buy some insurance. I'm taking a toothpick, dipping it into thin cyanoacrylate and carefully wiping the sides of the fret slots, allowing the glue to soak into the end grain. I'll follow immediately with bits of paper towel pushed into the slots with a clean toothpick, and removed to wipe off any excess. I don't want to change the width of the slots, I just want to get a little glue to wick into the grain to find any cracks or other defects that remain.
On the face of the fingerboard I can be pretty sloppy. I have a test tube with a little thin cyanoacrylate mixed even thinner with acetone. I'll wipe this stuff on the edges of the fret slots to soak a little glue in from the top. This trick REALLY works!
Only problem is that I have to work super fast. If I really hustle, I can only do about 6 frets per batch of thin glue. It seems that the acetone (or the water in the acetone) acts as a catalyst, and the glue starts to thicken in the test tube. No big deal, I'll just use a lot of small batches. Almost always I'll see the glue drain into little cracks I didn't even notice before. I make sure I fill these little guys with full strength cyanoacrylate before I move on.
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