We present new methods for painterly video processing. Based on our earlier still image processing technique, we "paint over" successive frames of animation, applying paint only in regions where the source video is changing. Image regions with minimal changes, such as due to video noise, are also left alone, using a simple difference masking technique. Optionally, brush strokes may be warped between frames using computed or procedural optical flow. These methods produce video with a novel visual style distinct from previously demonstrated algorithms. Without optical flow, the video gives the effect of a painting that has been repeatedly updated and photographed, similar to paint-on-glass animation. We feel that this gives a subjective impression of the work of a human hand. With optical flow, the painting surface flows and deforms to follow the shape of the world. We have constructed an interactive painting exhibit, in which a painting is continually updated. Viewers have found this to be a compelling experience, suggesting the promise of non-photorealistic rendering for creating compelling interactive visual experiences.