hi, dry skin huh, how often do u bath your dog? i don't think the shampoo is the main issue due to your dog dry and rough fur. dogs releases oil from their body and it is advicable to groom (comb) your dog everyday in order to spread it to the fur. That is y some dogs have beautiful and shinny fur and if u bath your dog too often then your dog will have rough fur. >Thomas<
yes, like others mentioned, the dogs shouldn't be bathed too often. dull coating is also due to the dog food and infrequent grooming (groom often to remove dead hair, will look more shinier also, like zack and mack said).
you ought to try out some medicated shampoos in the market and bathe the dog with warm water with it (so that the shampoo have better contact with the skin). also there are many supplements like oil and tablets for shiny silky doggie hair.
i did not bother to do all that all this while and ended up with a dog that sheds mountains of hair and rough, dull coat. it was only recently i took all these steps after my dog is diagnosed by a vet. now his is a happy dog with a sun silk hair :))