Me neither.
I like to leave the natural protective layer on. Ducks are such a messy muddy/poopy egg-layers I rather just do as least as possible.
I guess in my head I rather have some dried up poop on it with the protective layer on it, then no protective layer and some spores of bacteria somewhere.
Momma isn't cleaning them; so I guess I just not do that too.
I guess maybe it also depends on how many eggs you have, and what kind of hatchingmachine. I have 4 eggs in it now while there is room for 40. My hatchingmachine is made out of wood and cloth and not easy to make sterile.
If you have a LOT of eggs, close together, and thus a LOT of eggs that can conteminate each other, in a hatching machine that is easy to make sterile, I would probably do it.