How to stop flaky and dry skin on my dog?

One of my English Springers has an issue of dry, flaky skin.
Presently, I do give him a dose of fish oil each day as well as olive oil in his food.
I make both my dogs their "veggie meat gravy" which I put over dry food.
It is just very strange, because Nikki does not have this issue but her brother does and they both eat the same diet. A genetics thing, I guess.
They are on FRONTLINE, so I really don't want to use any kind of shampoo on him.
The vet is old school and said to feed him some bacon grease. I don't cook bacon in my house, so that one doesn't work for me.
In any case, I would be curious to learn from other dog owners who have experienced this same issue and how they resolved it.

used different kind of shampoo and give them a bath with medical shampoo for dry skin.

No, you have to use OATMEAL shampoo. He/She might be allergic to something!

give your dog oil in his food. itl give him/her a shiny coat and nice skin.