Buy a different brush that he does not recognise and start to do a little bit each day, but stop when the cat gets annoyed. Do it really lightly (even if its not actually doing much brushing!) to start with, until he thinks its like being stroked and he will like it, then over days/couple of weeks get firmer. I always hold the top of the fur when trying to pull the brush through a tough knot as this releases the pressure where the fur is attached/pulling to his body!
Try not to get angry with your fluffy cat. I had a fluffy kitten who didn't like a brush and my mum looked after him for 4 weeks and it ran away because she tried brushing it every time she went near it
Good Luck