I just pulled a couple of my guns out of the cabinet that don't get shot very often. I found rust on 1 of them, on the barrel and vent rib. Not bad, no pitting, but it left some color difference. What is the best way to remove this without hurting the finish? There must have been some water drops on it or something before I put it away. I am upset with myself for letting this happen, now how do I fix it?