Brewer's yeast will work for his skin and coat. It will take a few days to get in their system but it will perform miracles. I have 3 of my dogs on it and their skin is great.
You can buy it at walmart or buy it at GNC in powder form. Give it atleast 3 days to really start telling a difference. Watch to make sure he is not allergic to yeast. Hope this helps!!! It has me!!!