This seems to work better. The UVs are very dense, so painting a texture in the traditional way in GIMP with the exported UVs as a guide is quite hard. That’s what I did in the last image I posted. This time I basically texture painted a splat map in Blender, and then pasted photo elements over that in GIMP without using the UVs at all at that stage.
The process now is to use World Machine with a layout generator with a circle (broken up) as shape guide to an Advanced Perlin node (device), also with a radial gradient as a mask input. I then used a thermal weathering node, and finally an obj mesh output.
In Blender I UV mapped with Project from View (after hiding all non-visible verts), created an image for texturing (set up in the Shading layout of course) and texture painted different colours for the rocky part at the top and the soil-like skirt around the base.
Taking that into GIMP I pasted rock photo over the top part and an appropriate soil texture (from the same kind of rock formation) over the bottom part. The junction needs some work but the process is pretty straight forward.
I’m pretty pleased with this workflow. I’ve never been happy with procedural rock textures, or procedurally generated image textures such as produced in Substance Designer. Actual rock photos are the way to go I think. At least for me.