Hey bhduxbury,
It is perfectly fine just use hand brake on level ground (i.e. garage). Since there is no ill-effect leaving in gear when the engine is off, it is a good practice.
Over the years I have read so many horror stories about running away cars, because the drivers forget to apply adequate hand brake. This often happens when the driver is preoccupied. Therefore I always encourage others to use gear when engine is not running. I also tell others that when start the engine, always depresses the clutch pedal even if it is not needed. I guess good habits always come in handy.
Cheers
