There are a lot of good grooming tip, ideas, and how to's in the wool rabbit and fiber arts section. For mats, I just cut straight into the mat, as close to the skin as I can without actually cutting the skin. Then I start brushing it out. It usually takes several cuts to get the whole mat out, but its the best thing I've found so far.
As far as combs, I start with a slicker to break up any pills on the ends of the fiber and get out any of the debris, usually that goes into a bag to use for nest material when breeding time comes. Then I use a rake style brush. This helps get out the loose fiber between molts. My lines are high producers, so I get quite a bit of fiber between molts as well. I work from the 'dust ruffle' and go up towards their back. Once that is over, I go around again with the slicker to get any stray hairs so they don't invest them and get wool block. Both he 2nd and third rounds go into my tub for spinning. Some people will argue you can't take care of an angora properly without a blower, but you can, its just more work. Also, when hey shed out every three months, I pluck the fiber by hand.
You can catch a lot more in the wool rabbits section. Check it out!
Hope this helps