Yes,clean before tumbling. I have done the black mess before. You will now have to wash all your pins, tumbler and brass in hot soapy water to get most of that slop off. I have a container of Shellite ( which you call Coleman fuel) and throw all the cases in it and give a swirl prior to tumbling. That will get most of the lanolin off before tumbling. When tumbling the dish washing detergent will get the rest off. If not enough dish soap it will just go black. When you open your tumbler after a couple of hours, there should be some bubbles still. If not there was still to much lanolin on the cases and the lube coats everything and not held in suspension.