I would start soaking their feet tonight. I use a shallow plastic foot tub like container. Warm water with Epsom salt. Soak for at least 10 minutes up to 30 minutes. I've heard of some folks using a 5 gallon bucket and cutting a hole in the lid for the duck to stick their head out but can't escape. Dry the foot, slather on a thick layer of neosporin, bandage the foot. It's good to do this every 24 to 48 hours. If the bandage gets wet between soaks, it'd be best to change it. Keep the duck in a smaller area with soft grounding. Within a few days of this, you should be able to pick away at the scab and pus. A hole will be left behind once it's all gone but continue to use neosporin and wrapping and it will fill in with healthy new skin.