I'd try taking the whole crepe iron down to the pumice scratch, then start buffing it out with progressively finer papers or stones.
Use the pumice (or whatever you start with) in one direction only, then each paper or stone 45* - 90* opposed. That will let you see if you're taking the scratch down evenly. If you do start with pumice and switch to paper (good idea), you could definitely use a finishing sander, rather than sanding by hand.
I'm not sure what grit pumice is, but I'm pretty sure a finish somewhere in the 150# (ANSI) neighborhood will be fine. Then reseason as though the finish were new, and use as before.
An alternative, if you know someone with the equipment, is to have the iron blasted.
BDL
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