In a previous life, I worked for a musical instrument maker.
I have filed, sanded, and buffed literally MILES of precious metal tubing,
as well as steel, aluminum, brass, copper, various species of wood, and
different plastics.
Here's my advice: Buy good files. DO NOT buy the cheap Chinese effluent.
They are worse than useless. Grobet is very good indeed, as is Nicholson.
Buy USA made, Swiss made, German made, etc.. They are NOT cheap.
Take some time and learn how to use files and take care of them. Your time
doing this will be rewarded a hundred-fold.
Here's a link to MSC Industrial supply - this is just one example of a vendor - and
a set of Grobet needle files. These are the best of the best, and worth EVERY NICKEL.
https://www.mscdirect.com/product/details/60304995
Good Luck!
-Stretch