Things I do different in winter.
Bedding in the duck house is deeper. As mentioned, it's good to fluff it, it dries out better.
Bathing water only once a week (or longer) on a day that is above freezing. The pool is smaller than in summer. It gets filled by bucket instead of hose. Some days I will chop the ice off the top. When it freezes solid I flip it upside down, the sun warms the plastic and the ice chunk falls out.
I found the Ducks do so much dunking in their water they are constantly breaking the surface ice. I no longer used a heated waterer. I give fresh water in a deep bucket 2-3 times a day. I bring the bucket in the house overnight so it doesn't freeze solid. I dump the dirty water down the toilet so I don't clog my drains or create an ice rink outside. I fill the buckets in the bathtub instead of the outside spigot.
I used to have a heated dog bowl. It didn't last one winter. I'm not sure if this is typical.
I live in a cold climate. It can drop below freezing any night of the year. We had our first snow on the mountaintops this past week and leaves are starting to change. We go months with frozen ground and long periods where it does not rise above freezing.
The ducks don't seem to mind much. They seem to tolerate the cold much better than the chickens. I am no longer surprised to see them hunkered down sleeping outside after dark in the snow. They don't wait for it to warm up to come out of their house to eat. They rarely use their house. They don't try to hop around the snow, but walk right through without hesitation.
I do not insulted the duck house or chicken coop. I do not supply supplemental heating or lighting. I do have a small solar powered motion light that helps me check on everyone after dark since it gets dark so darn early and is often still dark in the morning when I care for them before work.