I brush only after I pick the main tangles out by hand. It is MUCH easier to get the tangles out if you meticulously go a hair at a time. I might run a comb through to get a start at the tangles, or use it to keep some of the hair together, but generally I go by hand.
If you ever have to use scissors to get a mat out (most mats are caused by dead hair that had fallen out), don't cut across, cut DOWN towards the groud. This will help save as much hair as possible and loosen the mat so that you can work out the attached hair a hair at a time.
If you keep this up(say in your grooming routine), you will not have to spend much time on it.