One very important tool in my shop is my LED flashlight. It’s most important use is for finishing. It has two light levels and a focusing ring that allows me to focus the beam from wide too very narrow.
I wished photos could be shown here, but the only way to really see what a raking light can do for you is to try it.
The low beam wide angle is great for showing raised grain (even after raising the grain with water and sanding) and dips in the surface from over sanding. Then I wipe on mineral spirits and use a focused high beam to see areas that need to be filled or further sanded. Everything from machine marks to snipe, as well as gaps in edge banding, will jump out at you when using a raking light. I keep a pencil handy during this process, circling or marking the areas that need further sanding or filling.
The use of a raking light is essential in getting the best finish possible, and in the end, being satisfied with your project.