In his painting titled "Living On the Edge", William Powell demonstrates the use of painting knife with lots of step-by-step photos. Powell says: "The theme of this knife painting centers on the tree perched on the ledge. The hard-edged detail of the tree against the softly blended background mist creates scenic depth. Careful color mix control, overlapping objects, misty haze effects, and close value changes all add to the atmospheric feeling of the painting."
Note: To begin first step of tutorial, click link at bottom of intro page where it says: "Click here to Tools and Color Palette" and link at bottom of next page, and so on.