I applied Nustock to a rooster with some particularly bad legs one week ago. He'll get another coat tonight. I couldn't believe the difference a day made, although I attributed it to the moisture of the Nustock rather than an instant cure type of job.
I wish I'd have taken before pictures. But, I can get a good idea on how long it takes for new scales to grow in. I'll try to remember to repost when that starts/happens.
On the subject of mites: I used spinosad on my chickens, thank to very sage advice I received from Azygous. I'll never use anything else if I have another outbreak (unless it didn't work, of course). Nustock and spinosad are fairly spendy products, but ease of use and speed (spinosad - one and done) of treating 100+ chickens was well worth it for me. No egg withdrawal helped.