If it's coated.. different story..but if there's a bit of dirt, no problems here.To each their own! I always find washing my eggs before setting gives me better air quality in the incubator and gets rid of any filth blocking the air holes on the shell.
. There is bloom that covers the whole egg..the bloom doesn't keep air flow from happening, it keeps it safe from ...the dirt. 
Would colored pencil rub off easily?Been there, done that.. pencil, as stated by others is not viable for long and quickly disappears.
When dry cleaning an egg.. I have used the scratchy side of a new kitchen sponge, very successfully.. dry dusted with another cloth afterwards.
Yes last minute labeling is "exciting".
I also do that for packing for trips, to move, make food.. etc. Basically I need to be in the moment, within my known time frame. I find life so fast that I dare not speed past.
Crossing fingers you get a couple of more.
Oh! Going to count.
that they’re pure!Good luck!!I set 3.
All ready to go!
