Given the fact that you need so many of them 15mm is the perfect scale for Zombie games. Here’s a tutorial on painting them.
painting
Painting Dark Age Figures Tutorial
Dux Homunculorum has a tutorial on painting dark age figures.
Weathering Metal Armor Tutorial
Kevin’s Miniatures and Hobby Table has a post on techniques for weathering metal armor. I’m going to use some of these techniques on my Lord of the Rings Orcs.
Camouflage Painting Technique
Santa Cruz Wargamer has a tutorial on painting camouflage on a Tau vehicle.
Painting Rust and Dust
Kevin’s Miniatures and Hobby Table has a good article on painting rust and dust effects.