Sindwiller: Cool method, although you have no control over how paint will cover the surface. You will have to find a logical painted surface to use as a mask. While with paint bucket it covers the surface based on light and it's height.
Jenn0_Bing: I updated the tutorial with a tip that in some cases you might want to use "Vivid Color" than "Pin Light". Also desaturating that layer might help.
-Method