I would leave it as-is (don't even paint it) and disclose it on the form,
and just find a different buyer. Or even find a different realtor if you
have to. To me it doesn't make sense to spend any money at all to improve
something you want to sell in "as is" condition. Some buyers might be
really picky and others might not be so savvy to water issues and might not
even care about it much.