Jono;
Try this link to get you started. http://www.ww2modelmaker.com/articlepub/GinoPoppe_Faces_article.htm
The other suggestion I would make is to pick up a copy of these books.
How to Paint Realistic Military Figures, first or second edition
By Lynn Kessler, Don Winar
Modelling and Painting Figures Osprey Modelling Manuals
by Jerry Scutts
BUILDING AND PAINTING SCALE FIGURES
by Sheperd Paine (Kalmbach Books, 1995, ISBN 0-89024-069-8)
These are just a few of the books I have on the shelf that I use on a regular basis to help with my figures.
I hope this will help you.
Cheers;
Gregory