So once you have removed most of the air cell from the egg,
Your goal is to just watch for those veins to receed and peel back that membrane a tiny bit at a time mostly working over the head area as long as it's safe to do so. Safe meaning no blood filled veins.
If they are yawning and chewing they are still absorbing yolk.
So don't get too carried away creating an escape route where they can pop out before they're ready. Just try to keep the membrane from sticking to the feathers by keeping it moist and keep that head and eye area free from membrane covering as soon as possible.
If the membrane does not get stuck to the duckling it is still possible for them to turn and sort of zip out on their own. If the majority of the air cell is already off they can just kind of flop themselves out.
Be thinking about finding a small tupperware bowl of some sort or short glass dish that you can put a Kleenex or clean paper towel in the bottom of it in case you have one come out with a little bit of open or exposed navel. You'll want to place it in a little bowl of some kind and leave it in the incubator to keep it from flopping around knocking other eggs around, getting stuck on its back, or exposing that open navel to any bacteria that could be in the incubator off of the other eggs.