There are probably better solutions but since no one else replied I'll give you a suggestion. Try Keynote. There are ways to draw lines that look like brush strokes and you can use build in methods to make them appear in various ways one of which may please you. Once you have this worked out you can export the animation as a QT movie. You could either render the entire short scene in Keynote with text and a background scene (probably easier) or you could figure out some sort of alpha channel that would isolate just the swoosh. Maybe possible but I'm not sure how to do that. In either case you can set a custom frame size to match that of your movie.