Chris Bacon wrote:

I bought one o' them they there Stihl Easy File Chainsaw Chain
Sharpening Tool things, and having thought "Oh it'll be carp", changed
my mind very fast. Get one. Very easy to use, very fast, great
precision result each time.

https://www.stihl.co.uk/STIHL-Produc...-EasyFile.aspx

You can get them lots cheaper.

Project Farm seemed to like the 2-in-1, if you can't justify the
motorised grinder type

https://youtu.be/BzmKwxfqjjQ