If you will use the search function at the top of the page, you will see this is a subject that has been beat to death. It really is just up to each individual person. Personally I DO NOT reccommend washing any egg, either for consumption or for hatching. Eggs are porous and they absorb anything that touches them. So I do not want to wash an egg with poop on it, knowing that that egg is going to absorb poopy water. I do however have a little trick you can try. I keep a coffee can full of clean play sand in the hatching house and I use that sand to gently scrub the filth off, ONLY if it COVERED in poop. Other than that, it stays the way I found it. It works better than sand paper because it is not as rough on them.
do not wash eggs until your ready to eat them. never wash an egg to go in the bator. you will remove the bloom. that helps to protect the egg.
search the topic. it is well explained on this site
I never did understand the "do a search" reply in a forum like this. You might as well cancel all the members and let it sit as a referance, not giving a new member who might have years of experiance answer a question or give new thoughts to an old idea.
I have experimented with this. I have incubated some eggs that I wiped off with moist paper towel and others that were dirty and I just put in my bator. I have had no noticeable difference between the hatch rates of dirty eggs compared to clean eggs. It is just another one of those do it whichever way you think works best for you subjects.
This is better to the new user, or new chicken owner, who is then instantly connected to many useful ideas, thoughts and points of view on the subject. If they then have further questions they are armed with the relevant information to ask their question.