Hey Jeeves,
I start off painting the whole thing black, usually lacquer. I then use enamels to build up the colors of the face. I'll put in the main colors and add the highlights as very well-defined streaks or lines or whatever is appropriate in a given area, and build it up a bit.
Then I use a technique that's not unlike drybrushing; I dip a good sized round into some enamel thinner and wipe it off, leaving the bristles slightly damp. I then whisk back and forth across the face. The small amount of thinner left on the brush will blend the stark highlights into the main color for a nice smooth graduation of tones. This takes alotta practice!
For the uniform, I'll start by drybrushing the appropriate colors (I use the old Polly-S paints for clothing as it's a bit more matte than most paints) and I build up the main color of the garments, leaving the areas of natural shadow black. Then I'll go in with a few lighter shades of the base color for highlights and touch up shadows with black pastel.
Finally, I go back in with earth tones (pastels) in the appropriate areas. (Boots, lower trousers or wherever it'll look good.)
This is a 35th figure, but I've used the same techniques on a 48th figure as well.
Sorry for the slight fuzziness on the photo. But I think you can see the results fairly well!
Fade to Black...