I am need answers to questions about hatching mallard duck eggs?

I raised Mallard ducks before but, never incubatored them. I have 12 eggs that came into my incubator at different times. So I know that you need to stop turning to egg on the 3th day before the 28th day gets here. How do I know which one with that be? Also, by candleing them that should tell me which is the one that is more developed then the others right? I should see the forming of the duck inside right? Then once they are hatch how long to I wait until I remove them out of the incubator into the box with light? Because I know that I will have some eggs in the incubator that will be in there and not hatching until later in time... PLease help me because my time is running out the ducklings will be here soon... It is very interesting to incubate and hatch the eggs very interesting. I enjoyed doing it.. Cotact me with answers please. Thanks Kayla