>>354866317
blender texture paint mode is the simplest, but yes it's finicky. I Once you get the hang of it from some tutorials, it's tolerable enough though, and you can always rough in the basics then finish the job in a 2d editor later.

There are some paid unity plugins which let you do the same sort of painting from unity's viewport, but I've never tried any of them. The heavyweight way of doing it is substance painter, or you could try armorpaint (open source, have to compile it yourself if you want it for free though).