I have found that if I change bedding ( pine shavings )in our covered run once a month and scoop up poop a couple times daily our eggs seldom have any dirt / poop on them. If any just a tiny spot or two. I use a green 3M green pad to clean them (dry). I also use pine shavings in the coop with poop boards. I usually only have to change coop bedding spring and fall. Most times I can get a dozen eggs and not have to clean any of them! But you have to be diligent about scooping up poop every day! We are retired so I have the time! 
