My dog has a problem?

i have an argentino .. his previous owner didn't treat him well, he was left alone tied to a tree near a mountain of compost. so he got this illness in his skin and he lost his fur , and his skin became very sensitive and always bleeding , so i took him to a vet and he told me that i have to give the dog a shower every day and gave me powder to mix with water and put it on his skin , it kills bacteria ... i was wondering if any of you guys had the same problem ... what did you do about it ? and did the dog get all of his fur back ? coz mine didn't