I find a sugar/iodine poultice works the best and I (and others that I've told this too) have had great success with it. I learned this poultice when I worked at the vet clinic- we used it on horses with sole abscesses. Give it a try and let me know how it goes...
If the bird's foot is quite mucky, wash it under warm, running water. Don't soak it as you will be introducing more bacteria into the wound. If there is a scab and you are able to gently peel some of it off without causing a large amount of bleeding, then do so, once the scab has been under running water for quite some time. Clean out any visible pus (cheesy, gross looking stuff) and then rinse the foot once more.
You'll need granulated plain white sugar, iodine or betadine, coflex (or vetwrap, coban...), 2x2 gauze or 4x4 gauze (folded into thirds so it's the size of a large postage stamp), duct tape and scissors. Cut a 1 " wide 10 inch long strip of coflex bandage, and a 1/2 inch wide, 10 inch long strip of duct tape. Next, mix up the poultice - into about 1 heaping tablespoon of white sugar, dribble some iodine/betadine and mix. You shouldn't be able to see white sugar granules in the poultice, but you don't want it runny either. Kind of pasty - so you can pick it up and "mold" it in your hand, somewhat. Put a blob of this on the gauze. Put the gauze and poultice directly onto the foot. If there is a wound there from picking off the gauze, the bird may flinch, but the sugar/iodine can go right into the wound. Holding the gauze on the foot, begin wrapping the coflex strip around the foot, going between the toes and around the back of the foot (above the hallux, or back toe) but not up the shank of the leg. Once you're finished, repeat the wrap with the duct tape. Make the "shoe" tight enough that the bird isn't going to lose it immediately, but not so tight that you're cutting off circulation. Once the foot is wrapped, they should have a little shoe with their toes sticking out. The poultice works very well at drawing out infection. Change the shoe every day for the first few days, then you can leave it on for a couple days at a time. THe iodine will soak into the foot, leaving the sugar behind. The iodine will work its way into the infected area, killing bacteria, while the sugar draws fluid out of the foot (as it does when you put it on fruit- draws out the moisture). Sugar is also antibacterial and can be used topically on many different types of wound.
If the foot is severely infected, you can put your bird on Penicillin G Procaine at a dose of 30 000 IU per kg, once per day, IM or SC. Clavamox drops work well, too. However, often the poultice is enough and hopefully you don't need any further medications.
Hope this helps
Laura