Do it in short segments.. either when she's sleepy or part of a patting
session.. heep lots of praise and treats

Like your own hair, fur sheds.  but since the fur is so thick it can't fall
out and it starts to tangle..

Invest in a wide toothed comb... I particularly like the one I got at
target.. the tines are metal and are a good distance apart, to help pull out
the loose fur.  If she is in very bad condition now, your best bet would be
to take her to the vet, have them do a lion cut where they shave all the fur
off, and start fresh.  Grooming short fur is a lot easier, and as it grows
back in, hopefully you'll have made it a good thing for her so she'll take
to it easier.. or you've got a lot of lion cuts in your future.  Matted hair
is very bad for the kitty.can cause all sorts of problems.

If he is matted badly, your vet can "knock him out" and clip him - allowing
you to start from scratch, probably your best bet.  Also, I bought from pet
store an undercoat brush - great for animals with dense coats, gets out a
lot of the dead hair.  You can try that for regular maintenance, but won't
help you with the current situation.