There are....alot of things going on there..

First, and not to be insulting so forgive me. With proper cooking methods all you should need is a Green and Yellow Sponge that are common in grocery stores.

Hell, even with improper cooking methods ahem, my roommate, ahem the worst I have had to do was use some elbow grease with the Green Scrubbing side.

There are other ways, such as using Red Wine Vinegar to de-glaze the pan while it's still on the stove. But that is next to last resort and shouldn't be done during normal cooking with cast iron.

After either of these methods just dry and add oil with a non-lint cloth. Some people are snobs and say use "flaxseed" but regular Canola Oil or Peanut Oil work just fine.