In regards to all that was mentioned, it takes a modeler practice & patience to learn how to apply the right shade's & hilites in their respected area's of the face, and to blend them correctly.
I use Winsor & Newton artist oil's exclusively, and you also will find out that especially with 1:35 ....... a little oil goes a long way.
... Painting faces is not something you can achieve over night unless you are one of the exceptional few. You learn from self
trial & error. It's a very long winded technique to explain it all here and if you can find a decent figure painter, it is best to sit and learn directly by his/her side.
Also like the other modeler's suggest to pick up a good book.
I can recommend
Bill Horans book - " Military Modeling Masterclass " which is all about using Humbrol enamels & artist oil's.
http://www.amazon.com/exec/obidos/tg/detail/-/1872004091/qid=1040710930/sr=1-1/ref=sr_1_1/102-4127677-9111366?v=glance&s=books
Or
Lynn Kesslers new book - "How Paint Realistic Military Figures " ( Acrylics - Oil's - Enamels ) available through Kalmbach Publ.
http://store.yahoo.net/kalmbachcatalog/12240.html
GOOD LUCK
- ralph