I've been second guessing having 2 bantam cochins, as they are filthy. I have trimmed their butt and feet feathers, but I don't think I will be getting anymore, as I don't like them being so dirty all the time. I have a mostly covered run with rocks, but they still get really dirty.
Clean shavings/sawdust.... Its absorbant and if you keep the pens fairly clean it clumps the crap together so it isn't getting stuck to the bird's feet. If you have a bird with lots of crusted on, peel off what you can. Soak in soapy warm water, take a stiff brush, and work it off in the direction of the feathers.
Shavings are no good when the pen is open to the elements, tho, right? Id think they would get all gross and only make the mud problem worse. I live in oregon and it rains ALL THE TIME, so I have been having the hardest time trying to figure out what to have on the ground of the run to keep the mud down, but is relatively easy to clean. My latest venture is small rocks, which are great for the mud problem, but NOT for the cleaning issue. I've been raking them around about twice a week, but now they're just poo covered rocks, rather than mud. Ick!
Well cover the run maybe? Pearock topped with gravel for better drainage and to solve the mud problem? Rotate the space that you let them out on so that they are on grass only? Maybe stick with non-featherfooted birds? If they are birds that you plan on showing, put them up on wire or confine to a barn.
My regular non-feather-footed chickens get what I call, "toe-balls" in the spring when the ground is thawing and mucky. They are just lumps of mud that have dried into rock-like clumps on the chicken's toes. Makes walking hard, and breaks eggs. Never fails, every spring, I'm out there with a pliers, gently crushing those clods off the toes. I tried soap and water, but the clods are too hard. I have accidently pulled off toenails a time or two...they heal without a problem, just watch to make sure any bleeding stops before someone decides it looks tasty.