@ZipLine-- I think that's okay for adult dogs, but I wouldn't give a puppy any supplements.
Usually, brushing relieves mild dandruff, especially if the dog has dry skin. My Labrador had this problem for a while. After I started brushing and grooming her regularly, the problem resolved. I think brushing encourages their skin to produce natural oils, which relieves dandruff and itching.
If the problem lasts for a long time though, it's a good idea to get some medicated shampoo from the vet.