Wait, you were using soap on a cast iron skillet? Like, for real, soap? I thought that was the cardinal sin of cast iron care, right up there with leaving it in the sink to rust. I've got a few skillets that are older than me and I've never touched them with soap, just hot water and a stiff brush, then dry it on the stove. The salt and oil trick is solid though, I do that for stuck on bits and it works way better than any scouring pad. Also, if your eggs are sliding, that means your seasoning is on point, so keep doing what Carol said.