The black skin tone is sooo much fun and so easy.In fact is easier than the white one.The first thing to do when you paint someone is to take a good look...is the skin absorbing light or reflecting it.Usually the black skin reflects light creating so much great contrasts and undertones...you have the blue,the red,the yellowish,the reddish browns etc etc.What I always do is start with an undertone...and build on it.Same with afro type of hair.If you paint after a photo then make sure the photo has a great deal of contrast so will be easier for you.