I'm contemplating to make a yarn holder out of oatmeal containers. They have just the right size for such a purpose. The problem is the inside. I don't want to leave the cardboard untreated. I love to work with natural fibers and there is always the possibility of invading and destructive pests, so the containers need to be cleanable and not offer surfaces that allow such critters to hide or dig in (easily at least). I was thinking of covering the inside with washable contact paper or spray paints. But I don't know if it's possible to apply contact paper inside that shape. And I don't know much about spray paints. Are there paints that would be usable for this purpose? Or are there different alternatives that would serve such a purpose?