In preparation for reinstalling the neck, a thin piece of paper rubbed with chalk is inserted into each surface of the neck pocket and then the neck set in and then removed. Any high spots on the pocket surfaces are thus marked by the chalk powder.
It is then just a matter of sanding high spots on each surface flush with that pocket surface. The sanded high spots in the next 3 different views are the spots where the original finish overspray is sanded away. The wood was sealed before being painted at the factory and presents no problem sanding it down., which the factory themselves did to a nominal degree. The pocket now fits the neck to a much finer degree than original. A good neck / pocket fit, especially on the bottom surface, will conduct the strings > bridge > body > neck > nut > strings acoustic sound loop much better than a "sloppy" neck / pocket fit.
Notice that there is some black finish removed from the pocket front edges. These will be touched up with the rest of the cutaway horns inside paint touch ups (wrong lefty strap button, correct strap button capping, etc.).
The pocket is then rubbed down with crumpled wax paper to prepare the pocket for neck insertion.