Hiya, Allegorthmic community!
When I open my mesh in Substance Painter 2, it doesn't seem to recognize that I have 2 different texture sets. I use the first texture set as my main UV layout that is used for all maps except lighting, then the second set is to give absolutely every UV shell its own space so that lighting can be correct for Unreal Engine. However, Substance Painter is giving me a nasty crick in the neck because it is texturing on top of the 'lightMap' uv set. I know this has probably been discussed before, but I can't find the solution via google, so apologizes in advance.