Hi
@awkwardkale and welcome to BYC
I see lots of good advice already offered to you. But I would like to chip in my experience with deep littering.
I am in NE Florida on very sandy soil and both my duck coop and my son's duck coop are directly onto quarter inch hardware cloth [to keep out predators] on the sandy soil. So our duck houses drain really well
We use pine shavings [not fine ones as they are too dusty for ducks] in the coop.
But we also gather live oak/laurel oak leaves in March every year. These are put out by neighbors by the sackload for the county to collect. I am the early bird that drives round and collects them before the garden trash collectors get there!! If you have access to live oak/laurel oak leaves in the spring -- collect them and store them either in trash cans with lids or strong black plastic bags. Clean dry live oak/laurel oak leaves are an excellent addition to the bedding.
When the pine shaving bedding is looking wet [we do give our ducks access to water in the coop -- its possible to reduce the wetness by not offering food and water in the coop] we add a layer of oak leaves. Then continue the pine shavings on top.
In the cold months -- we do get some nights that are 32F and below in NE Florida -- we use pine straw. I put bales round the walls of the coop and break up a bale for the ducks to snuggle into in the middle of the floor. They rarely snuggle in: they mainly stomp it down!!!
I find I need to dig out the deep bedding twice a year and so make sure I do it in October so that a layer is building up again before the cold weather. The lower layers of bedding maybe damp but they are also hot as they have begun to compost. That is the beauty of deep layering -- the bedding helps to keep your ducks warm in winter. My son digs out more often -- quarterly -- as his duck house has a low roof [that opens to get inside and clean] and more than 6-8 inches of deep layer bedding leaves too little "head room". The deep layer in my duck house will get to 10-12 inches deep over 6 months.
When we dig out, we put our composting bedding into a compost pile.
I have separate rotating drum composters that I have to make sure the mix of brown and green is correct. But we just keep a pile for the duck bedding. My son adds lawn clippings. I do not as I don't have a lawn. I find the the duck bedding breaks down into good mulch [not compost] within 6 months. So that I can dig out the mulch and spread it on my growing beds, before digging out my duck coop again.
Our ducks free range during the day. I know people who have a confined run -- where the ducks have to have access to water even if they do not at night in the coop -- dig out their deep layer bedding from the coop and leave it in the run to absorb excess water and mud. even wet deep layer bedding is less messy than mud!! It will eventually need raking out from the run and putting in a composting pile