Any chance you could let us know what your skin tone recipe is please???
I undercoat with Halfords Brown Camouflage Spray. It's very dark and incredibly matt, which grips paint really well. It seems to be discontinued, but you can find the odd can still on shelves now and then. I save mine specifically for African skin tones now, but I used to use it all the time before it became rare.
My basic tone is VMC chocolate brown, followed by a mix of the chocolate with VGC beastly brown, then pure beastly brown and finally I add a bit of VGC heavy golden-brown to the beastly for a top highlight where I think it is needed (faces mostly, but also shoulders and the occasional knee cap).
I kind of wish I'd gone for a darker palette, using buff to mix with the chocolate brown and highlighting a bit more selectively, as the shilluks are from the Sudan and skin tones there can be incredibly dark.
Thanks for all of the kind comments.