Thanks for the suggestions. After thinking about the look I was after I went with some cold blue and applied it last night. It turned out great! Because I had polished the bare steel the cold blue didn't absorb very much (not that does very well anyway). Any sharp edges and corners took almost no blueing so it looks like the pistol has wear. It turned out a nice "gun metal" grey, no pun intended. It looks like old steel with patina. It's a great use for cold blueing, I certainly wouldn't be impressed with the blueing if I was looking for a new, even, deep finish.