28 days for most breeds
minimum 60% humidity for the first 25
Duck egg shells are thin so they lose moisture quicker than a chicken egg. With this comes the increased potential of bacterial contamination in the egg. They tend to be more fragile and do not stand up to shipping as well as chicken eggs.
Trying to hatch duck eggs in chicken egg cradles often causes the egg to get stuck and then fracture when you go to remove it for the final stage.
They are easier to candle than chicken eggs.
Really don't know what your experience is here so it is hard to answer without further direction.
My best tip would be to find a nice cooperative broody hen.
Every 7-10 days I add duck eggs to the 'community nest' on the floor in the Frizzle coop. Every 7-10 days, I pull out fluffy little ducklings.
Haven't needed to use an incubator yet but your tips will come in handy if I do