A wire wheel will scratch them up pretty bad. Use a nylon brush. You can probably get them shank mounted for a drill, but mine is essentially a toothbrush with thicker bristles.
BTW, I have never seen ratchet knurling get dirty. It usually cleans up pretty well with a quick wipe down using a rag. Dirty knurling is common on older tools that have a sharper knurling on them, that get oily and greasy and collect dust to the point of turning into a dark cake.
Jim