Ministories has a step-by-step photo story on how to paint a regiment of American Civil War confederates.
painting guide
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.
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Painting Camouflage Pants
Studio McVey has a short tutorial on painting camouflage patterns on a pair of pants.
Viking Painting Guide
Crusader Miniatures has a painting guide for Vikings.