This may be a dumb question but you said it's unlit? So the lighting in the diffuse is only for that particular shot? It seems almost like a 3D painting.
Thanks for the comments! :D I'll upload some progress shots and the uv texture later for those who asked. Technically there's not too much to it though, it's only an unlit diffuse map. No special tricks, just look at the ref, get down and put those colors on where they're supposed to go, I guess? I did paint on the 3D…