My Dirty, Old, Pitted Tub! Keeping it CleanI have a very old, pitted porcelain bath tub that I can't afford to refinish or replace. It collects a lot dirt in the pits and I cannot get it clean. it no longer shines at all! It isn't stained, just has hard to remove dirt. I have done the bleach thing, Comet, various cleaners, even some from the janitorial supply house, throughout the years but nothing seems to work (scrubbing bubbles is the best) I have tendonitis in my arm and cannot scrub for long periods of time. If I do get it clean is there an economical finish or wax that I can use on it so it stays cleaner longer? Thank You!!!