Is There A Good Shampoo For A Stinky, Itchy Dog?

Great, @hillcritters, and I hope that this helps your brother's dog to feel and smell better. The video does a great job of explaining the hows and whys about yeast infection in dogs, and it really sounded to me like that was the problem you were having with your brother's poor dog.
As Remnant mentioned, there could also be fleas or ticks that are making him itch; but the telltale stinky smell is not usually found with something like fleas, plus if it was fleas or ticks, you would have been able to see those and dealt with it properly.
White vinegar is just a great natural cleaner and disinfectant, and it is very cheap to buy, as is peroxide.
I have also used apple cider vinegar as a natural rinse for my hair, and I think that would work for the yeast, if you have that and not the white vinegar.
Let us know how it works out, and if this does not help, we can try to figure out what else might be causing the problem.