I'm a fanatic about keeping my nestboxes clean to lessen the chance of getting dirty eggs. If I occasionally get one with a little dirt on it, it can usually be rubbed off with a dry paper towel.
If something happens to cause a really dirty, poopy egg it gets fed to the dogs.
I don't wash eggs using water until just before using them. Washing removes the bloom, a coating a hen applies to her eggs during the laying process. The bloom keeps out dirt and germs.
If you must wash an egg it's important to use warm water, approx. 20 degrees warmer than the egg itself. Using cold water causes the contents of the egg to contract, pulling dirt and germs into the interior of the egg. Warm water pushes germs up and out.
I also don't wash eggs before selling them and my customers prefer it that way. They know to wash the eggs just before using them.