Take things slow. I don't know what you're using to brush but my baby freaked out when I used a slicker brush. I tried it on my own skin and it hurt! We just use a metal comb now.
Do a little bit at a time and do it everyday. I think if your dog has knots it makes the brushing less enjoyable because it can hurt them when trying to brush the knots out.
Use treats and praise. Put him/her on your lap and brush. It takes time, but with baby steps, they might not learn to love it, but will tolerate it.
Good luck!
