I use the beauty parlor 400/600 grit finger nail files. About $1.50 each at local beauty supply places. An excellent gunsmith referred me to Sally's (Sally Beauty). I got strange looks when I went in there to buy hand fulls of the files. But they are perfect for removing the bluing. And every so often I clean the ends of my doubles with the 400/600 grit ones. He also taught me to use them to take down high spots when adding finish to wood, and you get a run that you did not see. Once they gum up they cut little, just enough to take the bluing off. Because they are flat they are perfect.
In grits from 600 on down to 100, two grits on each file.
https://www.sallybeauty.com/nails/ma...me%7CWhats_new
https://www.sallybeauty.com/nails/ma...me%7CWhats_new