Cleaning cast iron cookware
Jacquelyn has it right. But as one who occasionally buys seriously decrepit cast iron from garage sales, I can attest that some pans are so nasty that it's easier to start from scratch than to try to salvage the cure.
Definitely try scrubbing off the gunk. But if that fails just put them in the oven, run it through the self-cleaning cycle, and cure them all over again. Old cast iron takes a cure a lot quicker than the new stuff.
You can read the boards, but I can give you the quick and easy. Yes, use plenty of soap and a little hot water to remove the stickiness, let the soap do its work, too much water just rolls off the sticky pan. Start by using a scotchbrite scrubber sponge, switch to steel wool if you have to. Do not soak the pan, just get it clean and not sticky. Rinse well. It must be clean, not sticky at all. Dry immediately. Heat on top of the stove over med. heat for about 4 - 5 min., add just a little veg. oil to the bottom, spread it all around the bottom and sides, inside only, don't worry about the outside just yet. Remove from heat and let it sit overnight. Wipe/rub any excess oil from the pan with a paper towel until it has a nice sheen. If the outside is rusty/rough, treat it basically the same way. The method of baking in the oven with oil has only produced more stickiness in my experience. I have revived many pieces by using the method I have described. I hope it works for you, enjoy, I love my cast iron and use it just about every time I cook, which is often.