I am replacing old porcelain-lined steel bathroom sinks with Briggs solid porcelain. One problem: the drain hole has a rough contact surface and is larger than the old steel sink's. I purchased new washers to put on the drainpipes, but they're barely big enough to cover the hole, and too stiff to conform to the porcelain. My old washer is large enough to cover the hole, but is also too stiff. Tightening the nut only slows the leak, never seals. Are there any spongier rubber washers to fit porcelain sinks, along the lines of a tank-to-bowl toilet gasket? Is there some kind of sealant that could be spread between the washer and sink? Thanks.