I inherited a 14" cast iron Dutch oven from my Mom that has legs, a lid, and a long handle. I have heard it is called a Spider and may be a collector thing; but it sat semi-exposed on the parents' patio for over 40 years and is way rusted.
A friend, who writes D.O. cookbooks, said the way to clean it is to heat it to 500 degrees then use a wire brush on a drill to rub the rust off. After doing this thoroughly, put a light coat of Crisco on it and then season it. It may need more than one application.
I have not done this yet, but may get around to it on Saturday.
If you can, heat it outside on the grill. They have a tendency to smoke and stink up the house when you season them inside. A rusty one might not, but you never know.
I cooked a ribye last night inside and smoke was not much of a problem, used to grill steaks. Take steak and let it get to room temp. Put olive oil on it, and put a ton of sea salt and fresh ground pepper. Put cast iron skillet on burner and put on high heat til it starts smoking a bit. Cook 2 minutes on each side, will have a hell of a crust. Take olive oil that has been warmed with a clove of garlic, bast steak. Cook on rack over baking sheet, or roasting pan, anything that elevates the steak a bit. Then put in 375 deg oven for 25 minutes, take steak out when int temp is 140, and let rest for 10-15 minutes. Awesome steak, better than the grilled ones I normally do.
My advice on cast iron cookware is not to allow it to sit in a damp outdoor cabinet for 40 years. Helluva lot of work to get the rust and corrosion off. Heated the 14" Spider Dutch oven and 8" griddle to 500 degrees then hit them with the metal brush on the drill. Used fine brush at first, but coarse was much better. Returned parts to the oven when they cooled off a little. Probably spent 4 hours grinding off the junk.
We inhaled a great deal of rust dust, so anemia is out of the question for awhile.
Then scrubbed the parts with mild soap and various abrasive scouring pads. Oddly enough, the green nylon pads seemed to work better than the metal scouring things. We did not use Brillo pads. This took another hour or two. Never did get all the black, old seasoning off some places on the inside of the Dutch.
Seasoned them all 4 times in the oven for an hour at 350, each time allowing them to cool completely. Will cook some bacon and eggs on the griddle when the boy gets up. Used peanut oil once on the Dutch lid, but it did not work nearly as well as a light coat of Crisco.
It is easy to see why these long-handled 14" Spider Dutch ovens are no longer on the market. It weighs 25 lb and is very difficult to handle; a bail is a much better idea for anything so large.
Lard! And, I never scrub with metal. Just soak it in warm water to loosen up stuck food. Dry it on the stove to kill any bacteria. If you think it needs it add more lard when it's done.
I have a 100+ year old 12" skillet that belonged to a great grandmother. I only season it with lard. The longer chain fats produce a harder surface that stands up better when I get it white hot to sear steaks.
I have a newer 24 inch that I use when guests are over or if I do a big fillet. I keep it in the bottom rack of the oven and let it catch drippings and add lard every now then then. after a few years it's starting to look and cook more like the old one, good flavor. I normally use it on the outdoor burner I use for making beer, deep fried turkeys, crawfish, etc.
Honestly, after this post I started using mine a ton. I clean it with sea salt and water. It is already well seasoned. Last night I took a t bone and coated it with salt pepper and olive oil, then seared it after skillet was smoking, 2 minutes on each side, then I brushed tbone with olive oil that I had cooked with a couple of cloves of garlic. Then I put it on a rack and cooked it in a baking dish at 325 for 25 minutes, might have been the best steak I have ever cooked, and I used to grill them every time. Works well with salmon also, sear and bake. I hear that is what all restaurants do.
Just get the equivalent Le Creuset pan. Except for the enameled exterior, it is made from the same stuff, you don't have to season it, you can wash it with soap and you can pay ten times as much to own it. There's an outlet store down near San Marcos.