Oh, what have I done?!
I made a new recipe for salmon last night, indoors instead of usually grilling it, and it was disastrous for both the skillet and the stovetop! The marinade was harmless (no oil) but did make the fish not dry, and then I was to add 1 Tbsp oil to a cast iron skillet and get it really hot. Okay so far. Put in the fish (no instruction to dry it) and don't disturb it until it "releases" from the pan. This is about when I got into trouble -- it seared beautifully (and tasted great, too), but it spread detritus far and wide, and tho I can soak it off the counters and the smooth ceramic cook surface, I do not know what more to do to save the cast iron pan.
Long, long story ending: after rubbing with salt while still warm, there is caked on matter - oil? on the cast iron. Would re-oiling and baking in the oven help? Any other ideas? Thanks for wading thru this long explanation.