+1 on the Renaissance Wax. A 200 ml can will last a very long time. I apply it with a small piece of an old cotton T shirt and then let it dry. Buff it out with another clean piece of the T shirt and it will shine like new.
As stated, clean the gun first with Kroil and some 0000 brass wool rubbing gently to remove the rust flaking. (Remove the stocks before you begin.) Remember that you are just trying to knock off the rust, not remove the blue finish.
When that is done, clean with denatured alcohol and then apply the wax. Make sure to get it on the grip frame especially if you store the gun with the stocks on. Several light coats and buff like crazy. Reinstall the stocks and apply a light coat to them as well. Buff well and if any lint gets in the checking, remove it with a gentle brushing with a nylon tooth brush. (Don't tell the wife you used her toothbrush either, they get really funny about that)
That should keep your gun shinning and prevent any future flaking.