Here’s a nice — if not overly deep — painting guide to ancient and medieval armies.
painting guide
Painting A Confederate Regiment
Ministories has a step-by-step photo story on how to paint a regiment of American Civil War confederates.
American Civil War Painting Guide
Quindia Studios has a basic American Civil War painting guide.
Napoleonic Uniform Guides
The Blunders on the Danube blog has a large number of pages dedicated to the uniforms of various nationalities during the Napoleonic Wars. A neat touch are the photographs of figures the author painted.
Link
Painting Camouflage Pants
Studio McVey has a short tutorial on painting camouflage patterns on a pair of pants.