There are so many methods for painting gaming minis these days and so many specialty paint products designed to make painting easier with very respectable results.
For this wizard, John applied a basecoat of black and a light, top-down spray of gray to act as undershading. From there, he used the magic of drybrushing and mostly applications of Citadel's wash-like Contrast paints. A little highlighting here and there and that was pretty much it. Very approachable method for even the greenest of paint splashers. And if you don't have Contrast paints, you could likely get similar results with homemade paint washes.