[turretslug]

This sounds like one of those cases where 10 different people have 11 different approaches, but I'd be inclined to use just a trace of petroleum jelly, e.g. Vaseline, applied to the balls with a screwdriver tip, and a trace of light spindle oil to the point where the spindle enters the threaded bush- often there's a circlip here. A bit like clock mechanisms, rotary switches are best with just a sparing amount of appropriate lubricant in the right place. Otherwise, excess lubricant just becomes a dusty paste and may eventually seep into contacts, especially in warm-running kit.

I recently worked on a piece of kit with one of those co-axial rotary switch and potentiometer shafts, they had seized together and nothing would shift them- spindle oil, Gunk release fluid, heat, leaving for days. In the end with nothing to lose, I stripped the switch assembly to its bare mechanics and used an engine valve spring compressor to separate the shafts- there was a graunch, judder, judder and a very rusty inner shaft emerged for a thorough polishing, lubing and re-assembly. The fun of vintage kit....