Why are you cleaning their feet? I love my birds, but that's a little much.... my birds now have mud in their run at times (winter) and when they go up into their coop, they walk on sand or whitewash or pine needles...the mud dries and falls off never to be seen again, packed down into the litter, etc. or their feet are dirty....I mean, they'll walk in dirtier things than mud and do OK... And they clean themselves the next time they dustbathe. If you make sure they always have cleanish dry fluffy sand....they'll dustbathe every day and you don't need to worry about muddy feet at all....
I had this same problem with extremely muddy feet. And with the type of dirt in my area, the dirt clumps dried hard on the feet poking holes in the pads. I had to use pliers on my quails feet to break apart and remove hardened mud clumps before I put a roof on the aviary, that is how hard this dirt gets! LOL
They don't sleep on it, they sleep on roosts, so it really doesn't bother them
Sand provides thermal mass, so you can use it for passive solar heating...i.e. if the sun shines on the sand in the winter (southern exposure windows, and the proper overhang) it will help warm the coop. Also, the sand will retain heat from chicken feet if they stand still...or warm up if you use heat lamps in the winter....that's one of the reasons I love it in the brooder. I don't get high chick piles...they usually fan out just touching each other. Everyone then gets the benefit of the warm dry sand. If you've ever walked on a beach at sunset...the warmth radiates from the sand.... Might take a bit to warm up in the morning....
