Over-explained: How to Paint Normal Map Information in Substance 3D Painter

How to get past the infuriating "Mesh Maps are NOT PAINTABLE" message in Substance 3D Painter, and just directly edit your normal map information. This is very helpful for correcting baking mistakes or directly pasting new normal map information on top of your existing baked normal maps. This tutorial assumes you have already baked mesh maps and you just want to edit your normal map inside of Substance 3D Painter instead of exporting to some 2d image editing program.