I don't know if its any help or you are still interested but Daz 3d have hexagon 2.5 for free this month and this can import a 3d file and create a uv map from it. Export the map as a texture file and work on it there.
Alternatively, you can paint direct on model and then unwrap the uvmap.
It has pdf tutorials and user manual and i'm sure there are other resources online.
good luck
T