Sorry, don't remember. My radio has been working OK since my last posting.
Doing it only once will be difficult if you don't have access during full operation (and during full exhibit of the interference)
I took the lid off the radio for a while to be able to adjust the squelch during operation.
With the lid on, it is close to impossible to find the slot in the potentiometer.
With the lid on and if operational, you cannot use a metal screw driver for the risk of mis-placing the tip and creating a short to the metal housing.
It is a single turn pot, so about 300 deg total range.
I would make adjustments in 30 deg steps.
3U.