When you say it "foams up" are you talking about the cooking oil?I have one BR hen that had them. As soon as I got her, we sprayed her legs with cooking oil twice a day for 3 days. It's the easiest way we have found to smother them. The one we use foams up and really does a good job.
Did it only take 3 days of spraying to take care of the problem?
Did the scales slough off ... and how long did that take?