Salmon Oil, or Flax seed oil can help dandruff. Also soaking dry food in water can help, or feeding canned. What food is the puppy on? maybe switching to a better food, or a different protein will help, or even a raw diet.
Beneful is very very bad food, I wouldn't let my dogs even sniff that garbage. That could very well be the reason for the dandruff. Consider feeding a better quality food. Fromm, Acana, Blue Buffalo, Blue Wilderness, Horizon Amicus, Go! Natural, Now, Merrick, Before Grain, Taste of the Wild, First Mate, Addiction...
Do not feed anything you can buy at Walmart, or Grocery Stores... Iams, Beneful, Puppy Chow, Ol' Roy, etc. Anything made by Hills, Purina, and Iams are crap as well.
Now I feel bad. We are feeding Hill's Science Diet; it's an "Ideal Balance" formulation, a bit more expensive (so maybe better?) I see another Science Diet at the Vet's, which could be a profit-making item. I stood on my head reading all the ingredients on the bags and it gets confusing. What do you look for?
The link to the dog food reviews looks promising, if it's completely objective/scientific. You know how special interests sometimes get a hold of these things...
OK, I'll look at other brands in the future. No reason to go grain-free is there?
Or I'll just start cooking for the dog. My brother-in-law had a mini doxie and used to serve small amounts of chopped cooked chicken in its own broth over kibble. (Low cost kibble knowing my BIL, but he was particular about the chicken parts.) These "dog balls" got to be a family joke. They were about the size of a golf ball and the freezer was full of them. That dog lived to 18, outlasted her first human and the next caretaker continued with the same diet.
Recipes anyone? One dog I know gets supplemented with cooked frozen mixed veggies.
I know alot of people that cook for their dogs. There are books of recipes for home cooking, "The Natural Dog" for one. I think as long as you feed a variety, you're good to go. I feed mostly grain-free, but some of the foods I feed have grain.
For the same price as Science Diet, you could get some really good foods