I was given a nice old 10" cast iron skillet from the 1950's. Only problem is the former owner sprayed it with WD40 in his garage so she wouldn't rust. Any chance of bringing it back?
I know the OP already responded that he'll give it a try. But I just wanted to second third or maybe fourth putting it in a self cleaning oven.
Just wash it with lots of soapy water and place it upside down in the oven and let it self clean for three hours. In the end you'll have a clean oven and a clean pot. The oils in the WD-40 are not going to survive the 900 degree oven temps.