I'll remember that if I ever have a leg mites problem. (Which hopefully I never will).Skip the DE. Wash the legs in warm soapy water and gently scrub the scales with an old toothbrush. Apply a thick coating of castor oil, vaseline, vegetable oil, Nustock, or coconut oil rubbing up into the scales. Repeat this at least once a week until new scales start growing in. Another method recommended by this link to immediately kill the mites is to dip the legs into gasoline, allow them to dry, and apply a thick coating of ointment, such as A and D or vaseline:
https://the-chicken-chick.com/scaly-leg-mites-in-chickens/