[HartleyMBaldwin]

I'll be over here giving my cast iron skillet a good scrubbing with some steel wool to get all the black stuff off.

Steel wool takes way too long. Oven cleaner first, rinse and dry, then use a palm sander for the really hardened stuff.

[Robert A Cook PE]

13,000 rpm hand grinder with a rated stainless steel wire wheel disk
Gets that dirty black iron smooth and shiny!
(Wear your PPE. Double eye protection. Gloves, apron.)