As its name implies, a pin brush ($4 and up) consists of stainless-steel pins with rounded and often plastic-coated tips. This type of brush is strong on dense, curly coats but also works for breeds with thin, delicate hair (Yorkies, Maltese, etc.). It shouldn't cause discomfort to your pups while grooming – in fact, the ends offer a slight massaging action . . . feels nice on their skin and helps loosen hair, too!
Learn other breeds it's good for when you read more.
Pin brushes work best on pets with medium to long hair (think setters and spaniels). It's a great tool for introducing a daily regimen – after the mats are removed by thorough grooming, this tool fluffs up the coat when you brush against the direction of hair growth.