What ever you do, don't let hubby use kerosene! Impurities in the kerosene may cause stains and, more importantly, it's vapors are flammable. We're sorry, but there aren't too many alternatives. Try trisodium phosphate (packaged and sold as TSP). If the TSP doesn't work, you might want to try lacquer thinner. Test an area first to make sure it doesn't soften the varnish. CAUTION: Lacquer thinner has dangerous vapors. Wear hand and eye protection, and make absolutely sure there is plenty of ventilation. At the sign of even slight dizziness, discontinue use.