i have always used windex, and an old toothbrush.
i have never encountered a knob (from a CB radio you pervs!) that windex would not clean.
one thing that i dont see mentioned is removing the little felt pieces that are stuffed inside the knobs.
its there for a reason!
if you get it soaked, it can lose its "springiness?" and when you put the knobs back on the radio, they will push on too far and can scratch the faceplate.
so, first step is always to use a tiny jewelers screwdriver to remove the felt pieces. then fill a coffee cup with windex and soak the knobs for a while.
(how long depends on how "nicotiney" the knobs are LOL)
i take them out, scrub them with the toothbrush till nice and shiny, and dunk them in a glass of water.
then they get a spray with canned air and are put on a paper towel to dry fully.
the felt gets replaced and they go back on the radio.
my process may be more detailed than others, but people do love shiny knobs!
LC