Try some heat (as mentioned earlier) when removing the Monokote (or other plastic film). The covering film itself is usually clear polyester film ..... the color (pigment) is embedded in the heat activated adhesive on the back of the film. Once you get the clear film off ...... what is left on the balsa is just pigmented adhesive. You could probably get most of that off (enough so you can ignore the rest when recovering [unless using transparent]) by rubbing it off with a trim solvent soaked cloth.
Ed