Matt'smom, is yours glazed on the inside? Maybe that is the reason yours cleaned up easier than mine.
I can swear by oil to cure cast iron. We have a few cast iron utensils. If you look after them properly, they can be the best items in your kitchen.
My favourite knife is a rough wooden-handled saddlery knife, a boot knife. It has a blade of black iron and the handle really is rough. I think it cost about $2. But it does need ongoing care - when we use it, we IMMEDIATELY wipe it clean and dry, then strop it on the steel. Every so often husband gets out the sharpening stone and works the knife over a bit more. No knife is sharp enough unless you can shave your arm with it. But my boot knife - if you let it get wet and sit there, even for a few minutes, it stains the blade and also begins to rut it and blunt it. Cutting citrus fruit means the knife has to be wiped off within seconds or it begins to discolour. It is not a pretty knife, but it is one of my best.
mother in law has one too - she liked using ours when she visited, and so we bought her one. But old habits die hard and I've seen her - when she uses it, she leaves it on the kitchen bench ready to be washed up, maybe several hours later. And she complains that her knives are always blunt, especially that one. But since we've been cooking dinner down at her place every night, I'm in a position to look after her knife for her. I've grabbed it off the sink, wiped it down, dried it, stropped it then put it away. A few times she has stopped me and said, "I haven't washed that up yet," but I keep pointing out - this knife should not be washed up with everything else, all it needs is a wipe down."
For people like mother in law, wiping down black iron with oil after it's been washed up, is a good thing to do.
We also have a black iron wok. Again, the best for the job, because black iron heats up fastest, responds to changes in heat fastest. But if it's left even slightly moist, it also rusts the fastest. Plus any iron contamination in my food, and I get violently sick, so rust is a bad thing.
So what we've worked out - we wash up the wok (or cast-iron frypan) right away. Then we wipe it out with a thin film of oil, then we dry the wok or pan either in the oven, or with the residual heat in the hot plate. It drives out any water in the microscopic pores in the metal. And the oil protects. If the oil heats up and bakes on, it really does work like an enamel coating.
We have a time-share place and when we stayed there we got talking to the (then) caretaker, a dour Yorkshireman. He was very humourless, very suspicious of the laid-back Aussie approach, especially as it pertains to barbecues. They had a barbecue on site for tenants to use (we hadn't at that time) and the caretaker was complaining to us about the horrible state people left the cast-iron barbecue plate in - "they let it get all black! And oily! It's disgusting!"
We watched the caretaker scrub the beautiful black patina off the cast iron to expose the shiny bare metal. This place was right by the sea, lots of salt in the air to send the barbecue plate rusty once it lost its black shiny protection. A good patina from being oiled then superheated, can give black iron a smooth, shiny, black surface. That is when you know you did it right. But we couldn't tell this bloke, although we tried. But he began to look at us suspiciously, as if we had been the ones to contaminate the barbecue with oil! Nope - shiny is clean, they believed.
While we stayed at that place we avoided having a barbecue. We had been planning it, but knew we'd not be able to clean the patina off, in all conscience.
You guys have got me thinking about getting out my clay pots again. I wonder how my Moroccan lamb recipe will go, in the clay pot? especially if I can bake it outside in the pizza oven... AND use up some of our excess of firewood!
Marg