I did that a long time ago. It doesn't work very well. Not the least of which is because of the fact that features will disappear at a certian distance.
What makes more sense is to use the metal texture placer widget thing. The only problem is that it's needlessly complex.
use CEGs for metalspots!
get resources from the sparkling fountain of eternal life!
(in case stuff gets invisible due to low details/whatever you can still use texture)