It helps to add water to their feed so they don't have to mix it themselves. A mash is easier to scoop and swallow, plus they can choke to death on dry crumble (ducks swallow differently than chicks that need dry food). Then they drink more water and clean their bills in the water so I use their rinse water to make the next batch of food. They will still spatter on each other and on the walls of the plastic tub when they eat due to their swallowing motion but what they don't clean off each other and the walls rinses off easily enough. I take the tubs outside to clean them and water the trees with the fertilizer so it does not go to waste.
I also use shelf liners that clean up nice so they can be reused for awhile and they give the ducklings good traction to avoid spraddle leg. My tubs have channels in the bottom to collect spilled water so the ducklings can stay high and dry. A dog heating mat under the first stage tub adds heat and evaporates the baby duckling splashes to keep them from getting wet. When they are bigger they go into tubs with plastic mats that have holes in them so the mess goes through while they stay clean and dry on top.
I don't use anything that absorbs water because wet bedding makes a worse stink than the wet mess it absorbs and it is much harder to clean dirty bedding than to rinse out the tubs and shelf liner (with a quick scrub using antibacterial dish soap). There is also the risk of them eating the bedding when trying to clean up spilled food and that can be fatal. The bedding can also be kicked into the water and make a stink that way. I even use shelf liner for chicks because it is less mess and less waste but I know alot of people use shavings because they have not thought of using shelf liners.
When you raise ducks you have to embrace the fact that they love water and they bathe themselves frequently, unlike chickens that bathe in dirt. They are very clean birds if you give them bath time. I start with the cheap plastic paint trays with a ramp for tiny ducklings without any oil and then they get buckets and tubs of water before swimming in the bathtub. Their bills have combs that take the water right off as they fluff up their down. Trying to keep them dry is not healthy for them so they need water to drink at all times and to bathe in as often as you will allow them to get wet.
Avoid absorbant materials in the brooder and you avoid the mess and stink. It is actually that simple, although you do need to clean out the brooder tubs and not let the poop build up for too many days. I give the ducklings a bath, move them to a clean dry tub, and then clean out the messy tub. I raise hundreds of ducklings this way from April to October (I try not to hatch too late in the year so the ducklings will be laying when the flock starts laying again in February).
