Path of the Outcast has a nice illustrated tutorial on mixing a base set of GW paints to come up with OTHER GW paints. For example: Chaos Black + Sunburst Yellow + Enchanted Blue = Scaly Green
Painting
Priming With Gesso
Here’s an article on priming your figures with artists gesso. I’ve actually been using gesso to prime my figures since the late 1970s. I only use it on 25mm / 28mm figures, though. With my 15s, it is much more efficient to use spray paint.
Speed Painting A 15mm Vehicle
You don’t have to paint everything as though you were trying to win a Golden Demon. Here are a few tips on speed painting vehicles.
Painting Horses Tutorial
Kevin’s Miniatures and Hobby Table has a good article on painting horses. I have never been good at painting the beasts.
Lighting Your Workspace
Massive Voodoo has a tutorial on lighting your workspace.