I just hatched some ducks in my LG, and this is how I did it...
1) The bator was in my bathroom, for the extra humidity.
2) I had to fill ALL 3 water channels to get the humidity anywhere near the recommended 70%, plus add 2 wet sponges to the bator.
3) I laid them on their sides, since in the turner they seemed to high.
4) I kept the temp at
the top of the egg between 99-101, usually right around 100 (these ducks still hatched a day early)
5) I turned them 3 x's a day, end over end (rather than just rolling them) and misted them once a day. Since I had goose eggs in there as well, they also got cooled for 15 minutes a day, which did not hurt them at all.
6) I hatched at 98* and 80% humidity, because I simply could not get the humidity up higher.
Yes the kind of ducks you are referring to take 28 days. You should let the bator run for a few days before adding the eggs. With the LG, once you get it in the 99-101 degree range,
leave it alone!! The LG is very sensitive, and just a little bump on the knob can make the temp jump or drop drastically!! And don't worry if the temp goes down when you add the eggs, it will take a while for it to come back up. A general rule of thumb with the LG is to wait a full day after adding the eggs before making any adjustments to the temp. It will also drop when you turn, if hand turning, but it will come back up. Usually once you get the temps set you shouldn't have to adjust it.
When it gets time for the hatch, you will most likely need to add a lot of wet paper towels, socks, and/or sponges to get the humidity to the recommended 85%. I have heard that ducks need to have lower temps days 25-28 (like 98-99*).
Good luck on your hatch!! Remember, there are many people here that are happy to enabl....er,uh....help!