If its a really ingrained infestation, it can take a few months to destroy all the mites and allow the scales to heal. Be persistent and patient, and it should heal up nicely...
That is definitely mites, treat it promptly.
Vaseline works well as does dipping the feet in oil.
The mites will not be killed by a single application in my experience this process must be repeated about every two weeks for best results.
Orpingtons seem particularly vulnerable to this (although...