On 05 Feb 2018, Phil Allison wrote in
rec.audio.pro:
I only discovered fibre pens last year and am still discovering
good uses. Cleaning up green corrosion on PCB tracks from leaking
Ni-Cd memory batteries is one - then you need to clean the
residue off with a PCB cleaner spray.
Is this what you're referring to? I've never seen those before.
They look like they could be useful for a number of things.
https://www.amazon.com/Cleaner-RISEP.../dp/B071HW43DN