Spend some time perusing the various built up AFV models in various galleries such as www.missing-lynx.com
I think that ML has the best ones on the web. Note that AFV weathering is not what it used to be. Many modellers are pulling off spectacular and realistic results without the older method of dark washes followed by drybrushing.
Note the newer style that accentuates dust (light colored) in the recesses and the accents with chipped paint and rust streaking. Personally, I think that this is more realistic looking than the old Verlinden-Tony Greenland style of bright highlights acheived through dry brushing.
Here are a few examples:
http://www.missing-lynx.com/gallery/german/hetzer_blustig.html
http://www.missing-lynx.com/gallery/german/mbpanth.htm
http://www.missing-lynx.com/gallery/german/migpanthg.htm
http://www.missing-lynx.com/gallery/german/migtiger.htm