I used to live in Southeast Alaska where it rains all the time. The local rifle range was heavily used by people who didn't reload, so I would collect a lot of range pickup brass. Because of the rain, a lot of the brass would have mud or dried mud on it. Obviously the brass had to be cleaned before it could be used. Here is how I recommend cleaning your brass. First, buy yourself a Lee Decapping die and decap all of your brass. After they are decapped put your brass in a plastic bucket, put in a squirt of dishwashing liquid, cover with warm water (I do this in my bathtub so when I splash water out I don't get everything wet) and agitate with your hand to get everything as clean as you can. By the way, you'll notice I said to use a plastic bucket. If you do this with a metal bucket you had better use ear plugs because sloshing brass in a metal bucket is louder than hell! If the mud has a high clay content it may not wash off right away and you may need to soak the brass for awhile. Soak the brass in soapy water as long as you need to in order to get it clean. Dump the dirty water off the brass and refill with clean water. Keep doing this until the water comes out clean and the soap is all rinsed out. I have a big plastic pan that looks like a gold pan with holes in the bottom. I use that to drain the brass. You can use a heavily constructed collander too. Try to get as much water out of the brass that you can. Once drained, lay out a couple of bath towels on the floor. Dump the brass onto the bath towels and spread the brass to one layer with as much room between the cases as you can. Set a fan to blow across the brass. Depending on the temperature and humidity it may take two hours to two days for the brass to dry. Roll the brass around on the towels every so often to help the brass dry. Decapping the brass makes the brass much easier to wash and dry. If you don't decap the brass first it may never dry because water WILL go through the flash hole into the primer!
Be sure to use a special decapping die for removing the primers. Most die sets have the decapping setup in the sizing die. You don't want to use such a die for decapping your brass even if you set the decapping rod such that the cases aren't being resized when you decap them. No matter how hard you try, dirt and grit will get in the die and scratch the resizing die. This will cause your die to scratch and ruin every case you put in it. After you are done decapping your dirty brass, clean the die and your press well. You want to remove any grit that gets on your press, especially that which gets on the ram or in any of the hinges. Grit in these places will cause premature wear on your press which will eventually cause misalignment of the ram making it impossible to load accurate ammunition. I clean the decapping die and press by hosing everything out with lots of WD40, then following with something like Gun Scrubber or brake cleaner. After it is clean I relube the press with Break Free CLP or a good grease. (I still haven't decided if I prefer Break Free CLP or grease on the ram.) I will also put a light coat of oil on the decapping die too, and wipe off the excess. Sometimes I will use spray silicone on the decapping die to protect it.
I hope this helps.
Whelenshooter