I still have some fibre needles and a sharpener. This rotated the needle against an abrasive disc which was also rotated.
This page has a lot of information on fibre needles:
https://www.wardworks.org.uk/Gramophone/index.html There is at least one incorrect statement on that page: "...but repeated playing of 78's with a stylus will result in some wear to the records"
Technically correct, but any wear cause by a diamond or sapphire stylus tracking at 5 grammes or less is negligible. Fibre needles gave a softer and smoother sound than steel needles. They caused less damage to discs though I've heard that they can cause a sort of burning effect due to higher friction than steel.
"....and you sharpened fibre needles to make it soft again..."
https://www.youtube.com/watch?v=7fJmmDkvQyc