Parking Brake Adjustment from the AIM 65-66
1) With the car on a roll test rolls and rear wheels driven at 50 mph. Apply parking brake until a light drag is felt (10-12 notches on handle).
2) Operate for 55-60 seconds
3) Return brake handle to released position.
While I’m sure there are few that have a roll tester, the same can be accomplished by driving the car. If you don’t burn in the shoes they will not hold.