What is the best shampoo to use for dry skin?

I normally use Summerwinds,but I did use a few others, I'm not sure of their names now though.  The dog is a 12 year old shih tzu, and he's been on a prescription diet for many years now. He used to eat Royal Canin and had no dry skin on that. Sometimes he gets dry flaky skin now.

I was reading the ingredients on the Summerwinds and saw things like sodium laureth sulfate and sodium lauryl sulphate. I had Biogroom Protein Lanolin Moisture shampoo before.

I was just looking in my dogs' drawer and I have Ring 5 bright white for my spitz, and I was surprised to see it doesn't have any ingredients listed at all.

'Oats Fur Coats' by Kelco is marvellous.  In fact, I love the results of most Kelco shampoos.

You can get it here http://www.technogroom.co.uk/catalog/kelco-oats-fur-coats-shampoo-354ml-p-213.html

What about EFA supplements?  Aka fish oil.  They help my boy.  He does best on a 3-6-9 made from fish, borage and flax.  Fish oil alone doesn't seem to work as well for him but I think it does for most.

I used Coatex Aloe & Oatmeal on my mums dog. It seemed to work well, no flaking or dry skin now.

I contacted a local company that does all the natural skin products, so I thought they might have something I could use on him. The man there said he has a Doberman and uses Neem soap on it. He said its a natural product and supposed to be moisturising with oils in it.

So I might as well get a bar of that and try it. Its only about £5, so if its no good it doesn't matter.