To remove mats: Fingers are your first tool! Mist the mat with conditioner, then separate what you can with your fingers. If you want to save the coat, use a slicker brush from the outer edges of the mat, working it loose. You can also use a greyhound comb, using the last tooth, to slowly pull the mat apart. This must be done carefully and slowly as dematting can be very painful and damaging to the coat.
When you remove a mat , the hair becomes damaged or broken; the tighter the mat, the more damage. Hair that is broken or cut, will mat more than smooth healthy hair, as the different lengths grow. Severely matted coats (more than 20% of the coat, or very tight mats)should generally be shaved down and restarted.