Depending on how bad you messed it up I would try steel wool to get it squared away and then get some cold blue and follow the instructions to try and blend the scratches in and prevent more rusting. It may require repeating the process several times to get it close to where it should be. If that doesn't work to your satisfaction, you'll probably have to decide whether to leave it as is or go to a smith that can do a hot blue on the entire thing.
Last edited by Topgun 3006; 01-10-2013 at 04:02 PM.