I have used nail polish as "poor man's locktite" on screw threads.
I have been reloading since the 1970s and have not had problems even with my reloaded ammo twenty years old (I have been shooting up some of my old 6.5 Carcano and .303 Brit reloads). I did try sealing primers with nail polish, but quit after a couple of batches, asking why an extra step. But my reloads are stored under stable conditions of heat and humidity.