A tutorial from Thomas Havlik dealing with baking textures out of a 3D program, in this case Autodesk Maya, and 3D Studio Max, and then painting them up in Photoshop to finish up the work on them.
Painting Textures from Baked Textures – Part 1 (Maya edition) from Thomas Havlik on Vimeo.
Painting Textures from Baked Textures – Part 3 from Thomas Havlik on Vimeo.