egg washing/wiping

 I tend to wipe mine over gently with a damp kitchen towell if they are very mucky.  Sometimes if it is dried on and crusted (one of my aunt's hens is an egg eater and sometimes the eggs are covered!)  I have to rub a little harder. 
I was wondering about this and if it was OK so I will be following this thread with interest.

Some people suggest leaving the poo to dry out, then sanding it off with fine sandpaper!  It means you get rid of the muck without compromising the anti-bacterial bloom on the shell.