It's a little more than a scratch in the finish, its a little deep slightly into the wood right down beside the bridge. Is there any way to work on this other than a complete re-finish of the guitar. I've heard some say fill it with crazy glue and the sand and buff, but I don't know the right grit of sandpaper and so on to use. this guitar is a '97 Gibson SG standard, vintage cherry finish. any help would be much appreciated.