When you bath him ALWAYS use a shampoo made for dogs, you can use an all natural like one from here Espree
http://espree.com/productDetail.asp?id=101 , and when you rinse use a good dog conditioner. I use coat handler, or pet silk, mix your conditioner in a container of water and add a few drops of pet silk liquid silk, or silk spirits to the rinse. Do not put too much of either in the container. I use a plastic kool-aid pitcher and use just a few drops of the oil, and a small amout of conditioner and mix well. Then pour over the dog and leave in. The oil helps to moistuirize the sikn. After a couple of bathes his skin should improve. If you use too much, he will look oily in a couple of days, but that is not harmful, just rebathe.