I've been painting small figures as long as (maybe longer than) I've been model railroading.
HO figures -- both toy soldiers and railroad figures. and, like
Riogrande's friend, miniature fantasy figures (although these are 25mm,
which is more like 1:72 or S scale, and lately "heroic 25mm" which is
Paint: I've been using hobby acrylics as long as they've been
available (solvents in the enamels give me a whopping headache). These
days, I use ModelMaster Acryl and PollyScale. Make sure they're thin
enough to freely flow off of the stirring stick when you lift it from
the paint (this keeps brush marks from showing). If you need to thin
them in the bottle, use a thinner designed for that type of paint.
Tools: Light / magnifier (although I use a desk light and cheap
reading glasses). Hot glue gun. Brushes (see below). Strip wood or
scrap lumber. Hot glue each figure on a piece of wood before you begin
painting. Use this to hold the figure. I prefer this to keeping them on
the sprue, because it gives you something to stand them up on, rather
than having to wait for paint to dry before you can lay them down.
Brushes: As people have said, the best you can afford, and take care
of them. I buy mine at an art supply store, generally sable or taklon,
and they cost between $8 and $10 each. Clean and condition them with a
brush cleaner / conditioner (I use Mona Lisa Pink Soap) after use, and
never leave them standing on the bristles in a jar of water. Condition
and shape them after each use. For sizes, I use a 10/0 liner for large
areas, an 18/0 liner for smaller work, and a 0000 spotter for detail
work (buckles, buttons, etc.).
Preparation: Wash the figures in warm, soapy water, rinse, and air
dry. Don't touch the figure with your bare hands after you do this, use
either cotton or latex gloves. Then prime them with spray primer (I
use ModelMaster rattle can primers). Either white or gray works fine,
although gray primer will make some light colors appear much darker.
Let dry for 72 hours. I actually prime figures one weekend, then paint
them the next.
Technique: When painting, hold the temporary base in one hand, the
brush in the other, and rest the bottoms (heels) of your palms against
one another. This way, if your hands shake, they both shake together
and the motions are not transmitted to the brush as much. This works
much better for me than a stationary mount for the figure. Paint
"inside to out", meaning the most recessed details first, then the areas
on top. Don't worry too much about "staying inside the lines". Little
slips that are obvious under magnification really don't show to the
naked eye. Fix only the gross misses. Add a second coat if necessary
once the first is dry to the touch. Don't try to paint eyes, eyebrows,
or other really fine detail (more on that later). If you have duplicate
figures, take extra care to paint them differently (unless, of course,
they're soldiers and are supposed to look alike).
Finishing: Acrylics dry to the touch in a couple of minutes, but
they're not fully cured at that point. Let your figures dry overnight,
then apply a thin black wash (1 part paint or India ink to 8-10 parts
thinner). Apply this sparingly over your figure. It will settle in the
nooks and crannies and bring out details like wrinkles, eyes, pockets,
etc. If you get too much pooling in one spot, blot it off, either with
your brush or the corner of a paper towel. Let dry 24 hours, then coat
with a clear flat acrylic varnish I use the ModelMaster brush-on
variety, although you can use an airbrush for this step. Now, let the
figure dry for at least 72 hours with minimal handling, then cut it off
of the wooden base with a hobby knife.
I stress the drying times, because it's tempting to rush and add the
next coat before the first is fully dry. For model railroad figures
that will only be touched a few times, that's probably overkill, but for
toy soldiers or fantasy figures that will be repeatedly handled (and
flexed, too), it's absolutely essential.