How difficult is it to remove heel rub from cranks?

I suggest not removing the anodizing and

Back in the old days alloy cranks were did not get eloxial (electrolytic oxidation) treatments. One used to just shine them up with Semichrome to a high "mirror" shine. The trick was to finish them off with some cornstarch. Part of maintanance was to not just replace the grease in hubs--- grease back then would often go bad and racid-- but also to polish everything up to a high gloss.

The look is, however, quite different from later cranks. No only have the design patterns changed but also the selection of alloys. Many are much harder than they used to be and less suitable to high shine polishing.