Same here, I'm aiming to handle the eggs less - but I'm not sure it will have an effect -- except for things like when I hit one on the side of the incubator and cracked it -- or saw a star-crack in the egg and tried to patch with wax - which once long ago got me a hatch.
This time I had an early hatch and when I opened the little incubator to remove her, she knocked an egg out -- which went rolling and I caught before it smashed on the floor. the shell kind of shattered (it had already pipped)--- and there was a spot of blood on the membrane. I left it until the membrane started to shrink wrap and over a couple of hours with moist hot paper towels, opening the membrane etc. it eventually hatched to be a successful chick.
I do have a 'no helping out' rule-- but the chick would have been fine if the egg hadn't rolled out of the incubator and off the counter to be caught in mid air.... -- and I couldn't just watch her shrink-wrap to death due to that unlucky circumstance. Seems like there is always something.
Whenever I have a cracked shell or an oops that needs covering I take a half a shell from a chick that has already hatched and soak it in warm water for a few minutes- then its pliable and I can exactly cover over my cracked spot. It acts just like the original shell and doesn't allow the membrane to shrink wrap. I used to use wet paper towels but they dry out pretty quick and you need to keep opening the incubator to check and re-wet. The eggshell on top of eggshell works really well.
Trish