Bootie,
The guy who made the movie (my brother) actually
is an archeologist specialized in prehistoric times. He has all the fine tools you probably mean. But scanning a WWII battlefield goes a little different, and yes on very rare occasions you damage something a bit. The method you suggest only works though if you have weeks of time for every square meter.
This would work if you find the first signs of something more precious than old rust or signs of human remains (which I never have).
Also from the sounds of my detector I can hear what sort of artefact I'm dealing with most of the times. That also makes me adjust the way I dig. If you stumble upon an egg grenade or mortar shell, also makes one careful I can tell you.
Look at this movie that is centered around the discovery of a dead German soldier at Kapelsche Veer in 2000.
http://video.google.nl/videoplay?docid=7...8399287200