What I would do - Wash cast in warm soapy water
step 1 - Primer base coat. Light Gray. thin coat 1-2 coats will do. Just want something for the thin flesh to stick too.
step 2 - Water down some flesh tone, a little thicker than a wash. Apply, redo thin coats until good coverage. Let completely dry in between coats. If you use a hairdryer to dry it, let the head cool some before applying next coat.
step 3 - If some raised areas still show a little gray, dry brush some flesh on. Paint must be absolutely dry and set before doing this. Especially if you are using cheaper acrylic paints.
Step 4 - eyes, hair, eyebrows. I use a micro-pen for pupils and eyebrows.
Helmet - Primer than paint base color, dry brush the raised surfaces. That netting is really hard to free paint and have look good.