I have a Kohler gray porcelan sink in my bathroom and the bottom is now dull and staining. What can I use to reseal it without using sink paint?
Unfortunately, there's no spot fix for this problem. In a situation like yours where the porcelain's worn, it means the finish has worn off. So you either need to bite the bullet and refinish the whole sink with that "sink paint" you mentioned - enamel - or you need to replace the sink altogether. If you opt to refinish with enamel, check out the many colors available at www.surface-repair.com.