What to do for cat's dry skin?

Dry skin is generally a nutrition issue that you get when the diet isn't high enough in meat protein and fats. Check the ingredients of the food - there should be a minimum of 30% protein in it from a real meat source (not by-products and not gluten). If there is quality meat protein in the food the fat content will be appropriate. Feed the better quality food and you should start noticing a big difference in 2 weeks to a month.

One of my cats is prone to dry skin. I buy Comfrey Root (though Amazon.com) and make a strong tea with it. I apply it to the dry areas of the cat (while very warm), being sure to get it under her fur. Though she starts licking it off, cats tend to lick "with the grain" of their fur. Meanwhile, the comfrey is on her skin moisturizing it.

Comfrey Root makes a very slippery, non-greasy, moisturizing tea.