divingin
Gold $$ Contributor
That is why I am asking what would potentially do the least damage to the bluing ... copper, brass, bronze or steel wool (all 0000).
Sort of depends on what he wants to end up with: a decent looking finish, or a like-new finish?
Any spot that has a raised rusted area will also have metal pitting to some degree once the rust is removed, and that area will have removed the bluing. Removing the rust and touching up the surface treatment will get the finish color even, but the pitting will still show. If he wants a like-new finish, it will involve removing enough metal to remove the pitting (which of course will remove the existing finish), and rebluing the entire firearm.
All depends on how much he values the item (hard to put a price on a family hand-me-down's worth.)