I would like to know more about how to use the different merge modes in PI. I like to play around and see what effects I get with different modes, but I'd like to know why they do what they do.
And I would also like to know more about the different features of the paint tool, like how to add custom textures, and what is the eraser for (it doesn't seem to do anything when I use the eraser toggle button on the paint toolbar) and how to add custom tool attributes to the EP.