You will notice that there are 4 different skulls on this particular sheild and they all have a different purpose. You can spin them around and use different eyes and teeth, and so on. In this step I am going to use the one with the crack in the eye. This one is unique in itself as it has a gum line instead of teeth. I line it up with the skull outline I just painted. The only part that is exposed is the teeth. You can see that I have applied a darker coat for the eyes and nose. I do this by painting along the edge of the sheild and allow the overspray to drift onto the surface. I have applied a few extra coats along the top edges of the eyes and nose sections to give a deeper cavity effect. For the gum I have painted a light coat along the edge of the sheild along the gum line allowing the overspray to drift onto the surface. If you want to add some more detail you can begin to apply some freehand work This is when you become the artist. To add a bit more dimension I paint in some eyebrows. I do this by starting off in the dark section of the eye socket and painting a kind of c shape. I bring my airbrush further away from the surface as I go. I do this several times to build my stroke up untill I get the look I want. I never try to paint it in one go. I then apply a light blend around the outside of the eye sockets. I do this by painting along the edge of the already painted area. This creates a more solid rounded look. You don't have to stop there you could shade his head a bit more or create an outline around the entire outside of the skull.