Welcome to pets.ca, WarrenIA
I would have the same questions as Hazelrunpack. In addition, has your vet done a skin scraping yet (eg. is vet positive it's bacterial and
yeast infections)? Has the vet ruled out any sort of mange? What meds exactly are you giving your dog? Has he been fully
de-wormed since leaving the shelter (fecal samples tested)? Any signs of fleas?
If the poor boy is scratching himself raw, please don't rinse or apply vinegar to his skin...it's going to burn immensely.