You can do it in either AE or Photoshop. In AE use the paint tool and double click the layer then set your brush settings and you can paint on the image frame by frame. In photoshop you can use the timeline to step through the footage frame by frame and paint on it then export the final result. In photoshop you have a lot more control over brushes. If you have a tablet use the stylus and it will work very well for you. Good luck.