It's a way to meet that which is wordless that wants to express itself through you without regard to how it's going to look. The basic principles are:
listen to impulses, body sensations, feelings and allow them to guide color choice and brush stroke
follow your energy… feel and paint, more so than paint your feelings
honor what shows up even if you don't like it
be curious about the contrary voices within
move toward the resistance presented by unwanted and uncomfortable feelings rather than away, and to hold them as invitations to choose a color and move the brush