Do you have a power washer, or a spray nozzle that can generate some force? I'd spray out the box, then soak it again and rinse it off. The spray should get out a lot of the grit as well. I'd then give it a spraying with WD-40 - to get the water out, and after that dries, put a little silicon lube in.
From what T-Mar wrote about the Centeron, I think it wouldn't make much, if any difference with your friction system. If you're not satisfied with how the jockey wheels spin, or if they are worn, you could just replace them with new ones that fit the pin size. I strongly advise staying away from Simplex pulleys (just in case you're thinking about it) as even NOS ones tend to crack very quickly. Generic SunTour or Shimano should work just fine.
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