A lot of little dogs come into my shelter a horrendous, matted mess. It can make their behavior worse because they are in pain. While it may be difficult or expensive, I really think you should get a vet to do this, or very skilled groomer. If you don't know what you're doing you can really hurt your little guy, or get hurt yourself from him biting you. A lot of times the skin on dogs like that is really sore, and there might be actual wounds or who knows what under there. You don't want to aggravate that or make it worse. And that in itself might end up as a vet visit anyway.