Buster has doggy dandruff and his skin looks quite flakey and dry. Is there such a thing as dog moisturiser? He has special shampoo but it doesnt really work.
It depends to a large extent on what he is fed how his skin and coat look and by being dry and flaky it does sound as if he's lacking something. I'm sorry, all the shampoos and moisturizers in the world won't improve it for any length of time if he's not right inside so I would be looking at finding a food more suited to him.
Believe it or not, Chappie comes out well for that whether you like the smell or not (I don't!) as it's got fish oil in and dogs do seem to like it!
In Poodles it was always the old saying a good coat is Bred for, fed for & cared for, in that order. As MFH stated, feeding is very important and will show in coat & skin condition. If nothing has changed recently in your feeding habits etc a good shampoo to use is Tgel (the one for humans).
You should be able to get Chappie anywhere, it's one of the cheapest canned dog food you can buy, just add some mixer to it! Another tip is to feed a tin of sardines/pilchards each week, that will help too and dogs usually love them!
There are good dry dog foods too if you prefer. We use some by Kennelgate, they're completes and the dogs love them; they look brilliant too, people are always remarking on their coats which is nice; the only trouble is we have to travel to Shrewsbury and pick up a batch each time as it's not sold around here and we get through three big bags a week!
My terrier had terrible skin as a youngster - is now Amazing with a wonderful coat due to putting Salmon oil in his tea. That and Seaweed. Good luck. He is also one spoilt mut on Naturediet sensitivegold. He did have an extreme condition though and as he was a rescue we suspected it was more to do with what he had been fed than anything else.