The easiest method I have found for washing / shading figures is to use the ink method. By using artist's inks to wash your figures (Windsor & Newton or Higgins brands), you don't have to mix up anything.

Just paint your figures as usual. After they have dried, but before you seal them, simply place a drop of ink on the figure. Then dilute it with water and run your brush over the area of the figure to be covered. I usually use the "Nut Brown" color. I've known people to use "Peat Brown," also. The ink is inexpensive, easily available and seems to last forever.

After the ink is dry, seal as usual. I use Krylon Acrylic Clear Coat spray. This gives the figures a hard, shiny finish. Then spray over t his with Modelmaster Lusterless Flat to dull the finish down.