Here is the package insert information for using vetrrx (Poultry Formula) for scale mites:
"FOR LEGS AND FEET:
Use VetRx at room temperature directly from the bottle. Using a cotton swab, apply to scaly areas. Rub in well with swab or fingers. Do this every day, once daily, for one week. After the fifth or sixth day, scales should come off by themselves or with gentle hand rubbing. There after, apply to bird’s feet and legs three times monthly. Avoid soaking the feathers (Moderation use of VetRx will not harm feathers)."
https://vetlabel.com/lib/vet/meds/vetrx-veterinary-aid/
At this link, down at the bottom, is a little chart for treating various external parasites. This is from the book written by the owner of BYC. I do see that he notes Ivermec for scale so I am surprised about that

VetRx has the camphor in it. I think you could treat totally without the ivermec (never seen it recommended for scale mite before), however, and save the digestive system/immune system the extra strain.
http://www.dummies.com/home-garden/...ns/poultry-external-parasites-lice-and-mites/
In the link below, This guy has a nice rundown... some folks soak their legs in warm, soapy water and brush gently with a nail brush before the first treatment. This fellow uses olive oil.
http://www.greeningofgavin.com/2012/07/how-to-remove-scaly-leg-mites.html