Step 11: Darken in Hulk's nose and draw the bridge of it, which comes down as lines from the inner corners of his eyes. Give Hulk some frown lines that extend to the sides of his mouth.
Step 12: Tighten the shape of Hulk's mouth. He's going to be gritting his teeth, so draw some shading to the sides of his mouth and tiny lines that look like plus signs to show where his teeth come together. Draw his gums as a series of curves (like connected U shapes) below his teeth.
Step 13: Add two lines below Hulk's mouth to indicate his lips. Also draw in a couple of lines above his mouth for detail.
Step 14: Hulk's hair looks like a toupee on his head. The hair is a bit tricky, so this section about how to draw Hulk's hair is broken down into four parts. First draw the bit of hair that comes over his forehead. It's basically a bunch of curved triangles of different sizes. It doesn't have to be perfect; his hair is messy, so just draw them randomly. Use the image above for reference when drawing Hulk's hair.
Step 15: Now draw the back portion of Hulk's hair, which is essentially the same thing: random curved triangles.