[mrerick]

If you see any active rust going on, it's important to remove it before it leads to pitting.

The best way to do this is with well oiled 0000 steel or bronze wool on a well oiled surface. Lightly rub the surface and it should remove the iron oxide without affecting the bluing. Don't rub too hard or too concentrated in one place.

When finished, spray it with RemOil or a similar preserving gun oil.

The bluing is magnetite (another phase of iron oxide) and is harder than the rust which is why it stays on the surface and the rust comes off. It is possible to do damage with too intensive use of steel wool since under the very thin magnetite bluing layer it's still just steel.