1. I just use regular Argo cornstarch on my WM doll which is a shade or 2 darker than regular tan. The doll needs to be completely dry before application and a light dusting is all it takes, spread evenly with a big make-up brush. I do get visible powder streaks from time to time, but a barely damp cloth soon remedies that.
2. Mine are both tan, I also use Argo. When there’s a pronounced spot I found massaging it takes it away.
3. I heard someone once added cocoa powder into their baby powder for their darker-skinned dolls.
4. As long as it’s not the sweetened kind, cocoa powder is okay.
