Right then, I said on Facebook that I was gonna attempt a tutorial on painting faces. So here it is. I don't claim to be an amazing golden daemon winning painter virtuoso type person by any means so don't expect any of that blending nonsense or wet pallets and a million different brushes cos I'm just way too lazy for that.
Right well let's get started.
First off you need to get your little plastic dude primed. I've gone with black. 
Then sling a dark brown all over the skin. Also since its a space marine head I've drybrushed the neck bits with boltgun metal. You know, the neck armour bit thing.  
 Right then so after that's dry I use dwarf flesh (sorry don't know the new colour name) and basically highlight all the raised bits but leave all the creases, this gives the feel of natural shadows on the face. (And that's why you based the skin with brown. See? I'm not mad) 
After that's dry, I go over with elf flesh (again I have no idea what the new colour is) on just the parts that natural light would catch, so like the nose, ears, brow, top of cheek bones etc.  
Then all that's left is the hair and teeth, pretty easy bits these, just drybrushed the hair a few different shades of brown adding a bit of orange at the end to make it ginger and then being careful adding some bleached bone to the teeth. 
Note that I've left the eyes well alone, I don't care how much of a good painter you are, as soon as eyes are added, that monster brutal killing machine of an astartes you've just painted ends up looking kinda retarded, so just leave them. It still looks good. The only time eyes should be don,e is on psykers when your looking to achieve an OSL effect. 
So there you have it. Hope it helped.
If not............ then I apologise for my failure and I will commence face palm in 3.2.1. 

So till next time.......... OORAH!!!!!!!