So foolishly I let my reissue Danelectro '56 U2 sit in its gig bag unplayed for a few years while I was in college. I just took it out, and the frets are RUSTY. As in covered in brown rust. What do I do? Lightly buff them with 4-0 steel wool? Just bending the strings back and forth seems to remove some of it. Any advice is greatly appreciated!