I used a series of layers to build up the portrait that is very common in traditional oil painting. First, the underpainting in green/gray (the dead layer), then washes of color building up from dark to light. For more information on this look up "7 layer flemish oil painting technique".
This website is helpful: http://www.ehow.com/way_5459614_layer-painting-techniques.html
BIG NEWS coming up on the next post by the way! I won something! Hold on to your pinky toes!