Bright idea #2: An office supplies catalog led me to this one. There is such a thing as large sheets of paper entirely coated with the Post-It note adhesive. It seems to me that this may be usable as a masking material, since it should be pretty easy to remove without pulling off any underlying paint. You might have to restrict yourself to using markers, rather than paint, when using it. If you can print on it, it might be a way of producing brick paper and the like, signs, etc. What do you think? Any other ideas for this material?