On the Youtube channel EatTheWeeds, there’s a video about how he cleans off cast iron pans using an electrified water bath. Seemed like a pretty hardcore setup. I’d link to the video, but I’m on a computer that blocks Youtube. Otherwise, I think a wire brush would work better than steel wool. If you use a baking soda and salt solution, the abrasiveness of that would probably help, and I’m pretty sure baking soda helps to get rust off. Maybe squirt a bit of vinegar onto the baking soda, get it to foam up.