This is a picture from page 5 of this guitar's description pages, showing a scuff of white paint which I removed and camouflaged that repaired area to match the surrounding areas aged patina.
I used a small rag dampened with acetone to carefully rub the white paint scuff until the paint softened and loosened enough to be lifted gently with an Exacto razor knife (shown further below).
But notice that the seam between the top and sides has some paint in it's tiny trough and other small spaces where the white paint remains. I didn't want to be any more agressive with the acetone, and want to sand down some of the slight marks left by teasing the softened paint with the X-acto blade:
Now I will use the tip of the X-acto knife blade, and a piece of fine sandpapter folded into a sanding "blade", to clean the white paint out of the seam:
And voila, the white paint has been removed; But the fresh color of the seam doesn't match the aged patina of the surrounding masonite:
So I use a wood-staining wax stick (nail nole filler) to rub some stain into the seam in a controllable and reversable manner. I could also have used instant coffee as a somewhat reversible permanant stain, but the wax base also effected the masonite's texture and sheen to match the surrounding area's texture and sheen made by many years of hand & arm oils, sweat, etc. The wax smears onto the small surfaces in quite thin layers, and wax is very similar to hand oils for re-establishing patina, because the hand oils evaporate into wax themselves:
Adding a bit more stain in repeated rubbings until the color, texture and sheen match the surrounding area:
