[codefox1]

Lots of information has already been posted, and of course opinoins vary (no pun intended.)
If it is not too filfthy, open all the way, spray with tuner cleaner or deoxit, brush softly spray again, catch fallings with a paper towel, let dry overnight, and yes, oil the bearings/bushings with a toothpick of lithium grease, followed by a toothpick tiny drop of WD40, and you're all set. ANy rmaining dust can usually be cleared by a piece of paper between rotor and stator blades. If the paper sticks, that means the blade is stuck and the part will not work.

Have not heard any good things about ultrasonics for this purpose, but could be called for in certain situations. Dunno.