It will pull the dead coat out. Slicker brushes will take out the dead undercoat. Start on the legs and hold the outer hair so that you can brush from the skin outward. If it is not removed, the coat will easily mat. Use this technique all over the dog - legs, body and tail.
Dogs resent the tail being brushed so save it for last.
For fine-haired dogs use a natural bristle brush. Moisten the area to be worked with a good coat conditioner. For long-haired dogs use a pin brush if the coat is not tangled, a slicker brush if the coat is tangled. Start at the legs, again brushing from the skin out and brushing only a few hairs at a time. The secret to thorough brushing is to brush only a few hairs at a time.