I just went with
this and made a layer mask, tricky at first but you get the hang of it real quick, then Hue-Chroma options: Lighting at -25, Chroma at +10 to turn the grey into a warmer and more natural skin color, and
there you have it. There's still some problems I haven't figured out how to fix (grey wrist, part of her inner thigh looking like shit, etc) but it looks probably fine if you squint hard enough.
Might wanna up your game. Cuz there's a new brown skin enjoyer in town.
You can keep the piss thing, though