I'm not sure what your friend meant by letting the car jolt slightly. If you put the car in park ("P"), then there should be no jolt at all. At that point you've taken the load of the engine off of the transmission. If he's saying to put it in "P" and let your foot off the brake to get that "jolt" then he's got it backwards.
The proper way is:
- After coming to a stop, keep your foot on the brake pedal and put the car in "P"
- WHILE KEEPING YOUR FOOT ON THE PEDAL, pull up on the parking brake handle
- take foot off brake pedal and turn off car.
The idea here is that the brakes are doing the job of holding the car in place (especially on a hill), and not the transmission. Specifically, the transmission's "parking pawl". Although unlikely, it is possible for the pawl to become weakend over time from not using the parking brake and it could break off and cause your car to roll.
This is also why technically you're supposed to turn your wheels when parking on a hill - my wife had an old VW bug who's parking brake failed and her car rolled across the street and into a neighbor's yard stopping right in front of their living room window.
