[gundoc]

If your friend sanded or otherwise scuffed up the bluing prior to paint you can wire brush it off and have it reblued. If he didn't do any surface prep and just painted it you may get it off easily with acetone and soft rags. Use cotton swaps and/or plastic picks to clean out the engraving and tight areas. After that use a light oil and 0000 steel wool to lightly scrub the metal to remove anything else, degrease it and then oil it as you normally would. Since you live in the PNW try to do it all in one day to avoid any rusting issues.