Good morning, good luck with your duck. Several years ago I had a couple of chicken with bumblefoot and had to do the surgery. Hope your non-surgical treatment works for you.
I would pack it with this and bandage it and wrap it and if you have or can get birdie booties I would use them over the bandage. and change it every other day and keep them out of water/mud
Great suggestions in the above posts! You may need to do surgery on it, soaking may not be enough. If you try soaking, Witch Hazel also helps to suck out toxins. Good luck and keep us posted!