I had a labrador which got mange and fungal skin problems when he was a young dog. What a nightmare!
What was incredibly successful was putting him on the raw meat diet. Dogs need the enzymes from raw meat. Google it. Yes, it's expensive but so are vet's bills. If I ever had another dog I would not feed it tins or dried dog food. As Adieu states - too much cheap carb and protein from grain. Dog food is a scandal.
Benefits to my dog: amazing shiny coat, small non-smelly poos, never got fleas, calmer, more "bidable" behaviour. He never got rheumatism or Arthritis and lived until 13 and half.
I am not sure about vinegar. I never had huge success from apple cider vinegar. Keep it away from eyes obviously! I did use a few drops of Grapefruit seed extract (diluted with water) for his ears and that was successful though the ears got better on the raw meat diet.