How do you adjust parking brake on a Kenworth T600?

Kenworth T600s have automatic slack adjusters, so to adjust the brakes do this:

Hook the tractor to a trailer and park it on a level place. With the engine running and transmission in neutral, push in both brake release valves. Wait about five seconds to be sure the brakes are released. Press the brake pedal all the way down slowly--count to five while you're pressing the pedal. When it's all the way down, take your foot off the brakes quickly. Count to five and press the pedal to the floor again, release, count to five and press/release the pedal a third time. This really does work.