As my experience with trying to work with black spots always ended badly, I wonder if anybody managed to make them into something looking so natural, that it did not matter.
For those, who might have missed it in the other thread, this is what happened to my worst disasters
To start with it was a tiny black spot “under the skin”, and I thought I will just paint over it, but after baking couple of times it burst through the skin. The black stuff was crunchy, hard like a burned plastic. I thought maybe if I get it out, and fill it with the thickening medium and paint over … NO when baked there was just a hole and the black bits were deep and wide. I tried to get even more of it out , and put in some sculpy (?), but it did not stay. Then I tried to fill it with E6000, thinking maybe I will be able to paint over it and make it into birth mark - no.
The only way to save the doll was to get replacement arm, which I did get quickly with no problems.
I had others; one was Skeeter that I bought on eBay years after this kit was discontinued, so we have fairy called Primavera, who has oddly placed gem stones around her face, where the holes were. That is not what we can do with a baby.
I have reborned couple of hundred of dolls, and I had 4 kits with these spots; I guess that is not that many, but still, it is a concern and I am really interested how people deal with them.
I paint over them also, if they are on the limbs and I use air dry, no baking ever. I got a Tippy Murray from UK a few years ago, and had one on the face, made that a mole, BUT I am making toddlers. Not sure young babies would have moles? 
LOL… I thought I read that moles don’t come out till later? but Tippi’s Mom was ok with him having one.