-Skin-
Start with a neutral base colour, or one appropriate for the skin tone you're using
for this tutorial, im using grey (vallejo grey primer)
using white, apply to the eye area, at this point, going over is not a problem, we'll be fixing that later
this part is optional and entirely up to your own preference, and i know i haven't done it well here, using black, carefully pick out the pupil, correct with white if needed
now, using your base skin tone (for the purpose of this tutorial, im using ''Cadian Fleshtone''), paint the rest of the head, then carefully circle the eyes, correcting the over-white
now, apply some highlights (for this i used Kislev Flesh), depending on the face you're using, you'll want to focus on the eyebrows (how odd... i've never seen a marine with eyebrows!), the nose, the cheekbones and mouth
finally, as is traditional with me, the wash. for this i used ''Reikland Fleshshade'', using a very thin layer, apply to the recesses and anywhere else you want shading, and very carefully around the eyes, this will correct any remaining errors around the eyes themselves.