I put a drop or 2 of Oxine in my bator water. I think it may help the eggs and the inside of the bator.
I personally have set and had great hatches from dirt smeared eggs. Even ones that get a leaky egg above it in the bator have come out well. Not smelling like a rose, mind you, but I did not wash it off. Just wiped it.
I have gotten dirty eggs from sellers here on BYC and had a 100% hatch. I had no problem setting them.
I have never washed an egg to set but have picked up a few from mud (emphasis on mud) puddles and set them with good results, after wiping them down as best I could. I will pick off the poop but do not sand paper it for a fear of removing that precious bloom.
I have only had one complaint about dirty eggs that I have sent. I had wiped them off but did not wash them. It was raining and the bantam Cochins can not be taught to wipe their feet so the eggs were dirt smeared. The buyer had a cow! Insisted that they had to be washed and figured she would not get a good hatch. Probably not considering that attitude. Even sent me a photo, which I have kept, to show me how dirty they were. Like I did not wrap them.
They were fresh eggs, in good shape and the ones I set at the same time (always my policy) hatched at 100% here.
I'm with Lanae, they get dirty, deal with it. And she raises a difficult breed for many so if she can set them and they hatch then you know dirt smeared eggs do fine. Not to mention, I am sure Lanae has hatched many more eggs than most.