9 Automatic keyframes
I place the Playhead at the start and click the stopwatch icon next to Style. This adds a keyframe to the start of the animation. I press the down cursor key, which moves the Playhead to the last frame in the Timeline. In Layers I doubleclick the Pattern Overlay icon to open the Layer Style window. With my cursor in over the top left corner of the painting I drag the pattern effect several times down to the lower left of the canvas and click OK. There’s now another keyframe set for Style at the end of the Timeline Layer.