heat up your Dutch oven slowly on the stove and wash it hot with mild soap and water on the outside. it will take the smoke and grease right off and not hurt your seasoning. I use my D.o. in my smoker all the time and washing it hot cleans it up in less than 5 minutes. heres some more info from my Dutch oven cook books i have published.
Cleaning: Cleaning cast iron is really quite easy and simple. As the same principal with seasoning, there are as many opinions as there are cooks. The methods I have found to work for me, are written here to share with you. However, as you cook more and more with cast iron and camp Dutch ovens, you will find a method that works best for you and your style of cooking.
Right after I am finished cooking in my Dutch ovens, I like to use a spray bottle filled with a solution of 4 parts of water to 1 part of apple cider vinegar to clean and sanitize with. First, scrape out all the extra bits of food with a plastic scraper; then spray the vinegar solution into the hot Dutch oven and wipe it out with a couple of paper towels. Sometimes, I need to spray and wipe out the oven several times to get it clean. But, it works well and the cider vinegar has other uses as well.
Many people will tell you to never clean cast iron with soap and water. I have found this to be an excellent way to clean cast iron and, sometimes use soap and water myself. Be sure that cast iron is warm to free the food from the pores easily, and rinse the cast iron with hot water, very well, to remove all of the soap.
The last and most important thing to do after cleaning your cast iron is not applying more oil to the iron; but, to dry it completely over, or in a heat source, to keep it from rusting. When drying cast iron, don’t get it to hot. It only needs to be about 225o for the moisture to evaporate and dry out. Once the pot, pan, or Dutch oven is cleaned and dried, place a paper towel inside with a little of the paper towel going to the outside to “wick” out any moisture from inside the pot and lid. Be sure to store your cast iron dry, without oil to keep it from turning rancid.
Rust Removal and Stripping Rancid Seasoning: Many people I have met over the many years of teaching camp Dutch oven cooking classes have asked me how to remove seasoning that is rancid or how to remove rust from cast iron. Removing rust can be as simple as using an S.O.S. pad or can get as involved as building an electrolysis tank for heavy rust. I will tell you about two simple methods and for electrolysis information you can search the internet for one of many sites telling you how from A to Z.
There are two main methods I use for rust removal which are both safe and effective. The first is for light rust and is quick and easy, usually taking less than 10 minutes before baking on a new layer of seasoning over the pot or pan. Simply take a S.O.S. pad and scrub the warmed cast iron with the S.O.S. pad and rinse with very hot water. Dry with towels and place the iron back into a 500° to 550° oven and proceed with the seasoning instructions above.
The second is a little slower but does a great job on removing moderate to heavy rust. In a time span of 24 to 48 hours the rust is consumed through a chemical reaction between alfalfa hay and apple cider vinegar. You need a large non metallic tub like a Rubbermaid storage container or plastic barrel, some alfalfa hay or cubes and apple cider vinegar with some boiling water. Place a 1” layer of alfalfa hay or ½” layer of cubes or pellets in the bottom of the tub. Place the rusted iron on top of the bed of alfalfa and bring the layer of alfalfa to 1” over the top of the iron and inside the iron also. Lastly boil enough water to cover the iron 1” over the top of the iron. You want to use a 3:1 ratio of boiling water to apple cider vinegar. Let the iron set in the tub for 24 hours then the next day, take it out of the tub and spray it off with a hose and check it out. Scrub it with an S.O.S. pad and wash with hot soap and water, rinsing well. Toss it in a hot oven and follow seasoning instructions. If you have heavy rust use a steel brush on a drill and brush all the rust off you can then soak in the alfalfa solution. When the iron dries in the oven it is common to see a light orange powdery rust layer, this is normal and in not a reason to panic. Just Season the cast iron and you are ready to cook in your re-conditioned cast iron.
be sure to dry it in the oven at 250 for 30 minutes and let it cool before putting it away.