I need some help with textures Thread

I'm working on a mod right now. I am mostly competent with 3d modeling and coding, but I am looking for some help with learning 2d texturing. Substance painter doesn't fit into the workflow for the game I'm working on due to texture space size so I need to pack/stack my UV maps. Substance doesn't like this. Can someone teach me a bit of photoshop/gimp to get me going here?

Thanks