When filing string groves removing the file marks is a pain. To help ease that pain take Emory cloth in a medium grit (120), rip a 12-16” piece off the roll, rip a 1/8 x 3/16 wide strip from it, and then twist it to make it round (see picture). Then shoe-shine the final shape while smoothing the groves, sharp edges, and removing the file marks. Next, I follow up with old sanding belts from my 1” x 42” belt sander in 180, 220, and 320 grits,
This a 7” x 5/16 piece of medium Emory cloth (It shows better on the camera for demonstrating.).
Partially twisted
Fully twisted.
Emory cloth is used by plumbers to clean/sand copper pipe before soldering fitting and can be found in the at the box stores or plumbing supply stores. The is a huge quality difference in the cloth backing and durability between what is carried at the box stores and the plumbing stores, though the box store material will work. It works very helping to final shape the handles and fades on bows. 1” x 42” sanding belts in various grits also work but are not as flexible or as durable.