I have used a kiddie pool as a brooder, but last year switched to a long nearly clear sided box. It has a lid that I use between broods when I store all my duckling things in the box in my shed. In use, it is easier to move than a round kiddie pool, deeper and so I don't need to build a "fence" as the ducklings grow. And, it will fit in my bath when I have had occasion to temporarily move the ducklings from my Florida room. I bought a nearly clear sided rather than a solid sided box as my ducklings can see me through the sides.
I like pine shavings for litter, and i use textured vinyl shelf lining under the litter to stop the little fluffies skidding around and damaging their hips