Carefully storyboard the action for the movie, noting the timing of every key movement. If it's necessary to get an exact read on the timing, ask two friends to act it out on video. Convert the time to frames and mark the frame count on the storyboard.
Draw nine lines (for the torso and each unjointed limb piece) and a circle for each character and assemble them into an entire body (but still as separate pieces). Arrange the art into the key frames and save them on the timeline.
Use the program to fill in the between frames. Double-check the animation to make sure it is exactly how you want it. Render the animation and export to a movie file.