I gave away a cast iron skillet awhile back and I've been meaning to have a little cast iron cleaning session 101.
I remember when we first became married we had a cast iron skillet and at the time I felt everything needed to be soaped to be clean. I truly struggled for a long time with the thought of not soaping a pan and how could it ever be clean. That pan is long gone and I swore I would never use a cast iron pan again. I mean after I totally destroyed the pan I just couldn't understand why anyone would want to own a cast iron pan. Everything stuck and I never could seem to get it clean!
Fast forward to about a year ago when we decided a cast iron skillet was the way to go for camping. I really didn't want to lug around my all clad to the camp ground and after doing a little research decided cast iron was the way to go but I would have to conquer my obsessive compulsive disorder with the soap. It was baby steps to begin with. Then one day I gave in and accepted the fact soap would ruin my new pan I was not going there again!
Now I use my cast iron more then my all clad dependent on what I am cooking and it has a home in the oven.
Salt dirty pan well with about 1 tablespoon sea salt and allow to sit on the pan for about 5 minutes to soften grim. Then use a soap free scrub brush to scrub the baked on bits off of the pan. Rinse pan well with clean hot water.
Dry pan well. I like to leave my pan in my oven for storage. The other wonderful thing about storing in the oven is it cooks in the grease if the ovens warm and leaves a wonderful non stick finish...
Whatever you do NEVER use soap in your cast iron pan.
I AVOID placing tomatoes into my cast iron pan because the acidity removes the nice non stick finish.
ALWAYS make sure you cast iron skillet is dry to prevent rust!
One last bonus about cast iron is it adds iron to the food that you cook helping to prevent anemia.