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.
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.
Massive Voodoo has a tutorial on lighting your workspace.
If you were one of the ones who bought into Reaper Mniatures’ Kickstarter for Bones, here’s a tipsheet on how to paint the figures. They’re a new kind of plastic and some of the techniques you’re used to may not work.
This video is about painting orcs, but the techniques can easily be extended.