With ducks I think cutting the foot is so risky that I recommend other treatments. Will be back in a few.
Might want to try Blu- Kote you can find it in most feed stores it's works great! Keep us posted on the how you make out best of luck!!
If it is bumblefoot, you do not have to cut the bumble if it is small, you just need to either put triple antibiotic ointment (no painkiller) on the foot twice a day until it clears, which can take 3 or 4 weeks, or follow this advice from Haunted55:
On July 1st, I found one of my Pekin ducks with what I would consider a bad case of Bumblefoot. Both feet were involved and I'm ashamed to say, the only way I found it was she was limping. One foot had 7 and the other had 3. I was able to grab her and bring her into the house and put her into a warm bath to clean and soak. Two water changes later and softened feet, all I had time to do was paint the bumbles with colorless iodine, grabbed the wrong stuff, and put her into a dog crate in my house until I could get everything ready to operate and get them gone. Did I mention the thought of this scared me half to death?
Sad to say it took 6 days before i was able to get everything together and someone to help out with the 'cure'. There really wasn't much to operate on, even though I was prepared to do just that. No matter how much squeezing or prodding or soaking, there just wasn't anything more to come out, it was all on the scabs that were covering the sores. The swelling was down from the 'marbles' I saw when I first found them. I poured betadine over the ones I had opened and painted the ones that I hadn't again with the iodine and put her back into her crate with clean bedding.
The bumbles have been dramatically reduced on the Pekin with just the iodine application and the smaller ones totally gone. The heels being the worst are still showing infection and need for more treatment. tomorrow, I will again give a bath and pull/cut out the scabbing and treat with straight iodine this time. These spots are now flat or as flat as they should be considering the part of the foot they are on. I will still touch up the places that had the spots before as well.