The only problem with "working the control" to break up the dirt is that it might permanently "scar" the track that the "wiper" rides on. Think of it as rubbing a car that is covered in a dirty grit. While you can see the surface more directly now and it looks cleaner, a close inspection of the paint will show that the "grunge" has left little scuff marks behind. This is no different than what happens as you "break up" or "grind" the grit out of the potentiometer.
Like most other "quick and dirty" approaches, the results of rotating a dirty control rapidly are initially positive, noticeable and easy to achieve. There can be long term damage done though and the end result of that is ALWAYS more expensive than taking a "more correct" approach to solving the problem.
If you read the "sales blurb" that typically accompanies most electronic cleaning products, some of them make mention of "tiny scrubbers" and "lubricants" to help repair / protect / seal the tracks that have already been damaged by doing the "self cleaning" approach. A good can of cleaner is WAY cheaper than buying a new potentiometer or paying for the labor that it takes to repair it. Sean
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