From my thread in the 6mm WW2 topic: TMP link
I agree with several points others have said, but with some subtle changes.
I undercoat with white spray primer. I use automotive primer from the auto parts store – cheap and cheerful compared to hobby sprays, and works very well for me. I find undercoating in white helps lighten the overall colors (easier than re-mixing your paints for smaller scales) and also contributes to highlighting as the uniform color gets thinned on the ridges during subsequent steps.
Then the molded-on base around the figure's feet. I paint this the same color as I will use for the dirt on my stands (a craft paint in a dirty brown color called Mushroom). I do this early, and don't worry about other colors getting on it, as it is to represent dirt, and dirt colors vary. I also don't worry about getting some of the dirt color on the figures, as I'm going to point over it anyway.
I then paint the uniform color. Sometimes (I know, I know, but I can't resist sometimes) I paint trousers a different color from blouses/jackets, as national uniforms indicate. But yes, as others have said, paint everything in the uniform color(s). Everything on the figure, that is. Not the dirt around them. At least not on purpose.
I am among the dark-wash enthusiasts. Early. Right after the uniform basecoat. Helps make every detail more visible to me even as I'm painting. I use all acrylics. My preferred wash now is a VERY dark brown/green, but I have used flat black with good results too. I dilute about 10 or 15 to 1. Blob it on completely. Then after about a minute wick it all off with a dry brush. Even beat up the figures a bit with the brush. Helps bring out highlights.
Then if you plan to paint a lot of the webgear in your detailing, skip this step. If you don't plan to paint the webgear, do a dry-brushing with a tan or light green color. This will pick up much of the webgear. But also rifles and helmets and boots, etc. But that's OK 'cuz you're about to paint over the highlighting on those.
Webgear is next. If you have the patience use two colors for different items, great! But don't fret if it is exactly the right color. Tan, beige, or light green. More detail in the color selection is pointless.
Then boots and guns. Boots are black or brown (depending on the nation). Don't bother with leggings, regardless of national uniform. I've done guns in all black, but unless we are talking moderns with all-plastic / graphite guns I just don't like it. So I do brown stocks and gunmetal tips and tops. For my WW2 Soviets I did bayonets in silver. I know Russian bayonets were blued just like the barrels, but I do it anyways. You can't see that they are bayonets unless they are a different color from the gunmetal. They add "character" to my Russian riflemen.
Then flesh for hands and faces.
Then helmets. (OK helmets and/or hats). The hands and helmets are indeed the most visible aspects of your paintjob. Helmets are sooo important. Best if they are a distinct shade from the uniform. Even if the national uniform was trying to match the colors, metal will look different than cloth, so paint 'em a different shade. Usually darker. And if they are a bit more metallic (glossy) that's OK.
I use Acrylic Gel Medium to mount my figures on my stands. I use US Pennies as my stands. I basecoat with my dirt color. I mix a bit of the dirt color in the Acrylic medium to give it some tint, then I put about 1mm thick gel medium all over the top of a coin. Push the figures into it. Use a modestly fine brush to "mush" the gel up to and even over the edges of the figures molded-on bases so there are no gaps. Then put my terrain stuff (model RR talus, shrubs, static grass and flocking, in that order) all over it. The medium acts as paint, depth and glue.
When it has dried, turn and tap the coin's edge on the table to get the loose stuff off, and put 'em on a board for 2 sprayings of dullcoat. Like to let the dullcoat dry in the sunshine if I can -- makes a stronger more durable sealant.
I have progressed over the years. I still have infantry that was only painted the dominant uniform color (nothing else). Then I started adding faces and hands in flesh tones. Liked that better. Then I started adding black guns. OK that's pretty good. Then boots. Even better. Then helmets. BIG impact -- looks much better. Then wood and gunmetal rifles. Ooh like that too. Then web gear, trousers and blouses. LOVE IT LOVE IT LOVE IT.
Yep, it's a matter of time. And most of the time they are seen from 2-4 feet away. But I pick them up to place them and move them. So does anyone else that uses my figures. And every time I pick up a stand of my stuff and look at it, or another gamer picks one up a looks at it, it is a small jolt of delight for me. So when I can, I spend the time.
Your mileage may vary.
-Mark
(aka: Mk 1)