Hi George, welcome to the forum.

That glue spot should not be an issue as it will be under many layers of primer, solid black, and then many more clear coats. Glue spots are a drama when staining the guitar as the affected part will not absorb stain.

With the fretboard I have finished a couple maple ones and on the first one I used no masking and bought some metal fret polishing guides on eBay which are ok but you can still easily end up scratching the surface when polishing the frets with steel wool. Better alternative is to cut out a section from a plastic ice cream container that is wide enough to cover fret board either side of the 1st fret and cut a slot in the middle to allow the fret to protrude on it's own. This will provide better protection when it comes time to polish the lacquer off the frets.

Good luck with the build and will be keen to see how it all comes together.

Cheers, Waz