Did he check for fungal infections? Those are a possibility too...
Both of those sound like good steps. Omega 3 fatty acids are good for skin & hair (& quills). I don't remember details, but I feel like I remember vitamin C also being good for skin issues - it was something I was looking into for an old cocker spaniel with skin problems.
~*~*~ Kelsey ~*~*~
RIP my sweet Lily ~ 6/12/08 - 1/20/12