I just followed this procedure on my Colt barrel with a permanently attached brake. You'll need a Dremel, fiberglass-reinforced cutoff wheels (not the flimsy regular kind), a nut splitter (like
this one), a wrench with a section of pipe to use for leverage, masking tape, and some method to mount your barreled action in a vice without damaging it.
I wrapped the barrel in SEVERAL layers of masking tape to prevent damage if the dremel skipped off of the brake and hit the barrel. Cut a groove into the brake along the top, cutting all the way through it at the muzzle end. Cut as deeply as you can without risking damage to the muzzle of the barrel or the threads. Now flip the barrel over and do the same. Once you have done this, use the nut splitter to pry the brake apart. Mine took a fair amount of force, but there was an audible crack and the brake basically fell off of the barrel. As long as you're careful and patient, this is pretty easy to do yourself.