http://www.dummies.com/home-garden/hobby-farming/raising-chickens/bumblefoot-pododermatitis-a-chickens-health-problem/
Try the link above. There are pics.
I would soak it for at least 10, maybe 15 minutes in warm water and iodine. You may have to work with it but it should peel off. Once you do that, wrap it and soak daily until it closes up again. After it closes up keep it wrapped for a few days at a time. After a few changes another scab formed...
I have been battling with a HORRIBLE case of bumblefoot. After 4 months, 3 surgeries, 2 visits to the vet, multiple foot dressings, 2 weeks of antibiotics and a poor traumatized chicken who now runs at the first site of me... :(
I finally found a non-invasive cure using the donut dressing at...