What I do is soak my ducks foot in warm water with epsom salts twice a day - for about 15 minutes. My vet said you could add betadine or colorless iodine to the water every few days. You want to loosen the scab because it has to come off. I then apply neosporin. Once you can start to pry the scab off you will need to get the infection out from under there. At that point you'll need to spray it with something like veterercyn or clean it with iodine. Pack the area with neosporin (not the pain-free type). and wrap it really well to keep infection out and keep it dry. Because her scab is so huge, you probably need to contain her in a small area inside with you, or outside in something like a wire dog crate where she can still see the other ducks, and that you keep super clean. Can she even walk with that? I'm so sorry you don't have a better vet. Maybe you can say where you live and someone might know of another vet nearby. Did you go to an avian vet?