That depends on the effect youre looking for. You cannot \"shade\" black, because it is already kinda dark
, but you can put \"shades\" of different colors into recess to create an illusion of deeper shades. Colors could be differen, dark green, dark blue, violet or brown for example.
If you highlight with lighter hue of the same color or a complementary color you will end up with a very contrast scheeme.
Here are some \"black\" example I like
http://www.coolminiornot.com/139211
http://www.coolminiornot.com/52235
http://www.coolminiornot.com/109231
http://www.coolminiornot.com/84610
As for goblins. They look very good violet/purple glazed over black. What I saw once done to them before my very eyes. You take a goblin. Prime him black and drybrush skull white or bleached bone over - don\'t overdo it, you don\'t want this paint too thick. Let it dry and wash it with blue or purple ink/ paint several times. Then you paint skin and details to you liking. Whole procedure took about 15 minutes per goblin.; Wasn\'t golden demon but looked good for table top.