I connect the brake servo to chanel 3, and i use the "MIX" function on my radio (Futaba FASST 2.4) to "mix" the chanel 2 and 3. I set the EPA on chanel 2 to have full trottle and no brake and set EPA on chanel 3 to full brake but no trottle.
Also, i dissable the brake ( or set it to minimum) in your ESC.
Et voila