Brake cleaning fluid is good (is actually the same thing as buggy spray only cheaper). Yeah, oil is going to be absolutely cleaned out too, so lube the bushings. I never used anything on the comm just keep it clean as explained before.
Just think of the old bushed stock motors. Whatever you did there carries over to the silvercan as well. Doing it is a bit more difficult, but the principle is the same. Bush alignment, brush alignment, etc. etc.