What I did was put the whole animation in a 750x100 movieclip. This way, if I needed to change something on the main timeline it wouldnt mess up the whole animation. After that, inside the movieclip I created a layer which holds a square that is transparent so the movieclip wouldn't change size. Then I started my animating. I used the brush tool to draw. I also turned on onion skins to make it easier to see the previous frame.