If you are going to wash eggs, use water that is warmer than the egg, otherwise you push the germs through the shell into the egg.
The other problem with washing them is that you wipe off the natural protective layer, so leave it more susceptible to nasties. People that know, therefore, would rather buy eggs with a bit of dry muck on them than ones that look very clean but not shiny

And to reduce the incidence of dirty eggs, which you probably already know, but just in case others don't - make sure the hens have plenty of nice places to sleep so they don't sleep in and soil the nest boxes, and make sure the route to access the nest boxes is clean, to clean any mud and dirt off their legs as they approach. And of course, empty the nest boxes promptly, and keep them clean.