My Dobie has developed really bad skin. His skin is very oily and has dandruff. I've upped his bathing to once a week, which has helped, but the dandruff starts coming back within two days and his fur still feels oily on his back as soon as he dries off. I'm using a shampoo for oily dogs, but it's not helping his back much, and he's still itching constantly. I know that I'm bathing him correctly... I use to be a bather for the local groomer for over a year. Does anyone have any suggestions for an oily dog??