I have had good success improving the appearence of an old gun by cleaning it thoroughly, going over the bad spots with 0000 steel wool, and applying Brownells Oshpo according to directions. It blends well with the remaining bluing and darkens the finish a fair amount. It is also very durable. It turns a gun with a 60% finish into one with an 80% finish. I recently bought an old 16ga Stevens 311 with a fine coat of rust on the barrels. There was no major pitting so I went over the barrels with a wire brush until all of the rust was gone and refinished with Oshpo. It came out real well. I would not use this approach on a high value gun but for a common gun in rough shape it is an inexpensive way to improve its appearence while not changing its character.