The absolutely best stuff in the world is Buddy Splash from Cloud Star
www.cloudstar.com -- check around a pet store or a holistic vet may carry this product. It gets out every snarl, knot, matt - and smells wonderful & has natural ingredients
Everyone I recommend it to also raves about it. Also, make sure you are using the right type of brush for a yorkie - you need a pin brush. The best brush I have used is from Chris Christensen - I have the 20mm gold pin brush - what a huge difference than using a much cheaper brand. I would have never guessed a brush would be worth every penny
Chris Christensen Systems, Official Site, Internationally Renowned Canine Grooming Products Used By Top Show Dogs!