I lightly sanded a ferrule to make it smooth with the hosel. Now how do I make the ferrule shiney again? Probably the easiest answer that I can't find.
The acetone (nail polish remover) should do the job. Next time you have to reduce the diameter of a ferrule, just use a soft cloth with a "shoe shine" routine and that should do it for you. Again, a little acetone might make the job go a little faster. I use a soft cloth belt on my belt sander for the whole job. It only takes a few seconds to get the ferrule down to the same size as the hosel.