Get an old pot and hot plate. Put clean parts in the pot and cover them with old oil. Heat it up to 350 or 400 degrees and cook the parts for at least 2 hrs. Forget about ever painting them.
This is also an excellent technique for making cast iron pots and pans non stick, only use new vegetable oil or cheap olive oil, paint the pans with the oil, painting more on if dry spots appear, and bake 'em in the oven at 350 for two or three hours. And don't use soap when you wash them, just hot water- something I can't get my wife to wrap her head around.

arteacher--my wife has a whole set of them there cast iron pans. (Lodge brand) It's called "seasoning" them. She either did it wrong or used the wrong oil or something, but not a darn one of them is non-stick. I can't stand using them.

Not to mention the stench in the entire house from the baking process. Had to air out the whole house every time she did one.

They now come pre-seasoned from the factory.

Calcium Lime Rust, more commonly known as CLR, is a household cleaning product used for dissolving stains, such as calcium, lime, and iron oxide deposits, from material types found in western-style kitchens or bathrooms.

Its ingredients include water, lactic acid, gluconic acid, glycolic acid, sulfamic acid, citric acid, and surfactants. The product also contained phosphoric acid at one time, but it is now phosphate free. The phosphate free formula is slightly more environmentally friendly, but its effectiveness against some stains such as rust is greatly reduced.

Wash that nasty cast in HOT soapy water, wash it again,, then read about how to season it online. Dont worry about getting it perfect, just get one coat on it & start using it. Never let soap get on it & USE IT. iT WILL GET BETTER & BETTER.  Ditch aluminum & teflon & youll be better off.