I think I addressed what other files you need. As for protecting the finish - I don't. If you use tape it will prevent the file from cutting flush to the edge of the board. The secret is to us a really fine file and only light pressure when the file is riding flat along the edge of the board. The file will skip across the finish without cutting into it, while the file will snag the fret ends and cut them down. If there is any scratching of the finish it will be really minor and can easily be buffed out with super fine sand paper, abrasive pads, etc. It does require a delicate touch. The file should be pointing the same direction as the neck and is run along the edge. Do not try to do each fret individually - that's an invitation to gouge the board. After trimming to length, you can use the fret end dressing file to finesse the fret ends. You won't need to protect the fingerboard finish since the side of the file that touches the fretboard is smooth.