Detangler!
I have a 'Morkie' - Ella Bean and she has soft, cottony hair that mats up every day. Even when she goes 'naked' - playtime and wrestling with my other pup causes mats.
I use a detangler and I swear by Isle of Dogs Detangle Conditioning Mist. I spritz it before brushing her, which I do EVERY DAY, otherwise we both pay for it! It keeps the matting to a minimum, smells nice and unlike other detanglers, doesn't make her greasy or wirey looking. Its keeps her nice and fluffy! Its pricey, but its the only one I have tried that works, doesn't weigh down her coat or make it look greasy.
Isle of Dogs - No. 63 Detangle Conditioning Mist