[Radioroslyn]

I spoke to one of our engineers, an older guy, and he said there was (in the times of yore) some sort of spray in a can, that they called "the blue stuff", that was used to clean volume regulators and that was specifically manufactured for that purpose.
He said there is a small hole (so far I failed to locate it, but then I did not take the potmeter off) in the regulator, where the contacts are, and you just spray the stuff in the hole and then you turn the shaft several times back and forth, and that did the trick.

He said he would look, as he may still own a can of that thing, and if it is still there at his garage - we would give it to me.

Anyone knows what it i

Sound a little familiar from way back like the '60s.
Deoxit is good stuff. The others you mention will remove the resistance coating and destroy the pot. In a pinch Wd40 works ok. Some pots don't have a hole , you'll have to pop off the back cover.
Terry