I always use the "parking brake".
For safety reasons and to prevent brake cable freeze up.

As others have said, very few folks read their owners manual.
There is a wealth of info in there.
I read it because I am a bit of a gear head and I find good info in there.
Most folks would find it boring.
Perhaps the manufacturers should include a DVD with the manual as folks may be a little more compliant with this format...who knows?

 

Did the truck in question have rear disc or drum? I seem to remember that drum brakes by design would allow a vehicle to roll (drive) backwards with a minimal input of force (idle in reverse) regardless of the parking brake being engaged or not; you just could not roll/drive forward without significant force. I am assuming that the vehicle had rear disc just because of this.

 

I've been laughed at for using my parking brake on an auto. Better to be safe than sorry. But being said, I have had the problem when I go out to my truck to start it and it won't start because on the shift lever it says it's in Reverse, when I grab the lever to pull it up to park it won't go any further up. So I have to jiggle it around so it shows it is in park, then it will start-up. Remind you I have already had the parking cable lever and parking paw replaced once before cause truck got hung up in reverse and wouldn't even come out of reverse to where I had to have it towed in to get fixed.