Faces are painted very simply....
Total figure undercoated with black painted thined with Pino floor or klear floor polish.
after painting other areas I paint first accross the brow. leaving eye sockets untouched, then down each cheak very carefully. Then accross chin. and finally very gently down the nose.
Some people go further and high light this further with a lighter colour. I don't At this scale for table top it is enough.
here is an example of the best painting in FOW I have seen in my life...
note the Iron cross ribbons and 5 o clock shadow.

This is what we dream of being able to do .....