When he says "many times" it make take 30-100 times.
What you are doing is wiping/wearing away oxidation that has formed on the contacts of the volume control.
I used to have that on my maintenance list along with turning all the push buttons off and on 30-100 times.
Contact points need to have the oxidation cleaned off and many times you cannot get inside to do it.
This helps.
If that is your problem you will see/hear and immediate improvement and you will need to do the same thing regularly.
What you are doing is wiping/wearing away oxidation that has formed on the contacts of the volume control.
I used to have that on my maintenance list along with turning all the push buttons off and on 30-100 times.
Contact points need to have the oxidation cleaned off and many times you cannot get inside to do it.
This helps.
If that is your problem you will see/hear and immediate improvement and you will need to do the same thing regularly.