need advice on how to paint the face of an 1/35 soldier

What's your paint of preference? There's probably hundreds of good threads on the subject here, so you might do a search on it, but if everyone else is like me, they're happy to talk about their techniques.

Oils are my preference, so I can really only talk with authority about painting with oils. There are others who are handy with acrylics and would be of more help there. The process for painting with enamels is much like with acrylics, but most who could be considered very good use either oils or acrylics. Bill Horan is the only guy I know of who can get first rate results with enamels.

Every figure painter does his or her faces a little differently. As was mentioned above, the type of paint will determine general techniques. As asked, your question is akin to asking, "How do you drive?" or "How do I get to New York?" without knowing where you are or what means of transportation you want to use,
Post a picture of what you've done and maybe we can help you along your path to the dark side.

If you are painting the face of a particular model, I can provide antedoctal reference, in other words........If you are painting the faces of Marines in Afghanistan or the Iraq areas let me know. I had to put that paint on one too many darn times.
"Corporal Jack"

i always use testor paints.with that said,first get the basic skin tone your looking for then put a base down (paint the face with your skin tone)then decide what effect and era your going for (ww2 long term soldier would most likely have a 5o'clock shadow)then i use drybrushing to get that effect(if to dark barely get any paint on the brush wet and lightly go over ther dark spots because the lighter color won' t completely cover the dark..for the eyes use white first then with a fine point brush put the color of eyes in you want,mustache,eyebrows whatever. the gold secret is to buy a great brush you might have to spend 15-20 dollars for a good brush but it,s worth it good luck