My favorite tool for making smooth gravy is a flat whisk. Unlike the usual balloon whisk, it fits easily into the edge of the pan and allows you to loosen the flour and thickened gravy that collects there. The 8 sturdy stainless steel wires are strong enough to deglaze a roasting pan and make a roux, yet flexible enough to whip the lumps out of gravy in no time. Flat whisks are available in cookware shops and at many sites on line. You can find a selection of sizes at Broadway Panhandler.