I just bought a 870 Super Magnum Express. I got a great deal on the gun, but the guy I got it from keep it in his shop and it has a light coat of surface rust on it. What is the best way to memove this? I tried Flintz, but I didn't have a lot of success. The surface is rough not smooth. Any ideas before I take it to the gunsmith and let him have a go at it?