Big families, hard water and heavy traffic can leave tubs and showers a real mess. If they're fiberglass rather than porcelain, that means lots of rubbing and scrubbing that often does nothing at all.Though you've tried, that grungy mess just won't budge. So what do you do? Use a jackhammer? Dynamite? To whip up a special batch of our famous salt-and-turpentine cleaner, take 1-quarter cup turpentine and add 2 to 3 tablespoons of table salt. Mix well and then scrub with a stiff nylon brush. It's powerful, so be sure you've got plenty of ventilation. Don't rinse it away when you're through. Rather, use paper towels to clean up the mess and air-dry them out. Before you give them a toss, wash it with soap, then a coat of car wax. And that's the On The House tip for today.