Before you strip off all the old blueing, try this:
Take a nickel (as in a coin - the one with Tommy Jefferson's head on the front) and some gun oil. Soak down the rusted surface with gun oil, then rub the rust off with the nickel coin.
Don't make funny faces at me until you've tried it.
You will end up with a blue finish that has a "haze" in it where the rust has etched the polished layer. When rust on an older gun isn't too bad and is fairly uniform, I find that this can improve appearances quite quickly without having to re-polish and then re-blue.