“If everybody's thinking alike, somebody isn't thinking.”
Cleaning your cast iron after use is one of those things that is easier than many people think. As a bonus, if you use and take care of your iron properly it gets consistently better over time.
If you remember only two things from this post please remember:
1) Use your cast iron often. Frequent use improves the seasoning which makes the iron more nonstick. The improving nonstick quality is, in turn, going to make cleanup easier. Cleaning the cast iron properly will not degrade the nonstick properties and will make cooking with the iron even easier. It is kind of a Yin and Yang thing.
2) Clean the iron with the least aggressive method that will do the job. If a quick wipe with a paper towel and a rinse under hot water is sufficient then don't use a stiff brush and soap.
Use and cleaning are interrelated with cast iron. You should be giving your iron a nice slow warm up on a fairly low heat setting. Let a skillet warm up for 5 minutes at medium low rather than cranking the heat to high and trying to use it in 2 minutes. Adding too much heat too quickly to cast iron is about the only way to warp it in daily use.
Add oil to your preheated skillet right before adding the food. This prevents sticking which makes cleanup easier.
After cooking remember that cast iron stays hot for a very long time. Let it cool until it is warm enough to handle without a hot pad. Letting cast iron heat up and cool down slowly is important. If your cooking application requires rapid changes in temperature you should be using aluminum or copper. Horses for courses as the idiom says.
Most of the time all I do to clean a piece of cast iron is to run the hottest tap water into the piece while gently using a brush to remove any food items. I then dry the piece by putting it into the oven at 250 degrees or putting it on a stove burner set to low. Using heat to finish drying is critical for both removing all traces of moisture (especially for those who live in humid areas) as well as sanitizing the cookware.
Update: I now recommend woven plastic scrubbers over a brush. Same process, different tool.
You may be wondering about the use of soap. I think it is unnecessary for most cleaning and will definitely impair the early seasoning process of a piece of cast iron.
I think it is OK to set a well seasoned piece of cast iron in some mildly soapy dishwater if you just fried a mess of catfish and want to remove the odor. I would not do this with a skillet that is still developing a seasoning. (if a fried egg does not glide around inside a skillet it isn't fully seasoned yet) Adding harsh soap directly to the iron cookware and scrubbing it with a dishrag or brush will set your seasoning back (or flat out remove it) and may impart a bad flavor.
A better option than dishwashing soap may be plain old white vinegar. Vinegar removes odors, most grease and sanitizes as well. Add 1 part vinegar to 3 parts water and store in a spray bottle. When needed simply spray the cookware, wipe with a dish brush, rinse and dry in the oven or on the stove. Do not let the vinegar set too long as it can corrode iron. (You also need this vinegar spray to take care of wooden cutting boards)
A dishwasher should never be used for cast iron. The iron will rust in that hot, steamy environment.
Sometimes I use the edge on a silicone or wooden spatula to scrape out stubborn bits of food.
Here are four scenarios that should cover the range of cleaning challenges.
1)You've sauteed some mushrooms and garlic in olive oil. Nothing stuck so wipe out with a paper towel and rinse under hot water. Set the skillet back on the burner over low heat to dry.
2)You've stir-fried some flank streak and vegetables, a fond remains after deglazing. Run hot tap water and brush skillet until clean. Set the skillet back on the burner over low heat to dry.
3)You think your skillet is fully seasoned so you scramble some eggs but discover it wasn't seasoned enough. Lots of egg residue remains stuck to the bottom. Add hot water to skillet and let sit while you eat breakfast. Dump out water and add 1 to 2 tablespoons kosher salt and some oil and scrub the egg gunk out. Rinse well and set the skillet back on the burner over low heat to dry. Continue to use pan with an eye toward further seasoning.
4)While frying chicken in the back yard a hawk drops a dead muskrat into the hot oil. Consider using soap at this point.
WHY YOU DON'T NEED SOAP
This picture shows a Lodge 10.25" skillet after sitting on a burner set to low for 10 minutes. As you can see the temperature of the skillet is at least 50 degrees hotter than any nasty organism can survive. If you dry your cast iron on a burner or in the stove as I recommend they will be just as sanitary and safe as anything in your kitchen.
Seasoning cast iron properly, using it often and cleaning it in the least aggressive manner make up the holy trinity of enjoying your cast iron cookware. Once you master these you can count on your iron cooking well and lasting several lifetimes.
Another article I like re: cast iron care is this one LINK found on Cooking in Cast Iron.