From what I have read on this, it takes up to 30 days to heal. Servere pyodermas takes 6 to 8 weeks to heal. Give it time. It also said to give 2 to 3baths a week the 1st week. Second week 2 and so on. It helps to break up the scales so they heal faster.
http://www.merckvetmanual.com this is a good site on this.