The powder residue should wipe off pretty easily unless it's not been cleaned in a while. Any cleaner should work fine. Avoid anything made to remove copper fowling (usually any bore cleaners) as they will attack the base copper used in nickel plating and cause it to peel and or flake. Some are more "aggressive" than others, but best to avoid them in general.
"People live too long, dogs don't live long enough" - FTF Member-