Can't really help you there as I don't know what paint they use, but I'd use either acrylic with a medium or oil painting as it stay translucent. I know it's not the same thing, but I used to restore old 12" joes and used Cotswold replacement hands on them. The trouble was the hands were of a lighter color, so what I used to do was mix a very dark flesh color, painted it thick on the hands, let it dry for an hour or two, then wiped it off clean. It usually worked pretty well on coloring the flesh darker, so it might work for you.