The best results have been to wash the new cast iron in hot, soapy water twice until you are sure the waxy coating is removed. Heat the piece for 5 minutes to make sure it is dry of water. Melt some solid Crisco in a small pan and apply it to the warm iron with a clean, lint free rag, or good quality paper towel. Wipe off the excess on the edges. Excess oil will not carbonize on the surface and will flake off. Place up-side down in an outdoor grill (if possible, to cut down on smoke in the house) . Regulate the heat to 425 degrees and leave for 1 ½ hours. Turn off the heat and allow it to cool. Apply another coat of Crisco to the iron and repeat the process. You should have a good hard, black finish at this stage. A third coat will enhance it to a point that you can cook anything in the DO without concern.
I have cooked cobblers and several other dishes without a liner. Each cleaned easy with hot water and a plastic bristle brush. I wipe it dry and apply a light coat of Crisco while the iron is warm. Make sure to clean the ashes off the lid and treat the same way. You are ready to cook again.