How to get rid of, or control, puppy dandruff?

I have a 3 month old black lab. He has an access amount of dandruff and the vet told me to add just a very small amount of vegetable oil to his food a couple times a week....that was about a month ago and still no change. I was just wondering if anybody else knew of a way to stop or control it a little better. Any good shampoos or dietary supplements? stuff like that...