Once you have caught them make sure they are properly purged. While the Montana crawdads seems to be cleaner in general, the muddy waters in Colorado demands some extra attention to the cleaning of the crawdads. The Colorado crawdads are, depending on location, true to their nickname "mudbugs". After a couple of evenings of crawdad trapping I usually have 10 - 20 gallons worth of catch (yup, gallons!)
If you have an aquarium oxygen pump then you can safely keep the crawdads in water and just replace the water every day or so. They will shed the sediments and mud.
If you don't have a spare aquarium oxygen pump then you must not store them in water. Once the oxygen is used up the crawdads will expire fast. Instead, you can put the crustaceans in big plastic containers without water. As they crawl and move around the crawdads will scrape off all the sediments, well mud, that we do not want in our cooking.
For 3-5 days I keep the crawdads alive before cooking them. Every morning and evening I give them fresh water for 5 minutes and the rest of the day they rest in the cool basement of my house. As the picture show it is a big difference between day 1 and day 5.