This might sound alittle weird, i've seen people that used coca cola to help remove surface rust off metal surfaces.
The acid in it seems to cut through it, not sure it'd be practical to try on a driveshaft with some non-scratching scrubbing items to remove the rust in that method. As long as whatever you do doesnt put heat into the drive shaft to alter the shape or balance of the driveshaft, should be able to remove the rust from the driveshaft.
Depending on how much your time is worth and what the materials cost, you might end up looking into just buying one already done up and balanced.
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