For water in the large fowl coops that only have adult birds in them, we use heated dog bowls which work great! You can leave them outside in the run as well. For the bantams and young chicks and juveniles we set their waterers on homemade cookie tin heaters that have 40 watt appliance bulbs in them. We use electrical tape around the area where the cord goes into the tin to keep drips out. We just run outdoor extension cords to each of our coops (we have 6!) and each waterer is plugged into a thermo cube so they power on the bowls and tins when temperatures are 34 degrees and turn off automatically at 45 degrees.
We use pine shavings year-round for bedding and our roosts are 2x4's for large fowl, 2x3's for bantams set wide side up so that when the birds roost at night, toes are covered.
Our coops are also insulated and we have adjustable vents up high. Birds actually seems to do better with the cold than the heat from my experience. Keeping direct wind and drafts off the birds goes a long way to help them manage the cold temperatures, especially at night. We put up tarps on the sides of the runs that get the most wind (just secure with zip ties) and our birds do tend to go outside more often in the daytime in winter with them up