John. I use a dark brown wash (Burnt umber artist paint) for general use and a black detail wash only for prominent areas like the recesses around hatches etc. These vehicles got dusty very quickly, and the dark brown simulates the ingrained dirt and dust, whereas the black can sometimes be a little stark if it goes on a little heavy. When the wash has dried (a couple of days to let it really harden is good) lightly dry brush the vehicle using several passes of the base colour lightened with a little white (best colour for gray) each time. Be careful as the lightened colours need only to be touched on the raised detail and it is easy to press harder because nothing seems to be happening at first.
If you are depicting a vehicle that has seen some use, then use a little of the lightened colour around areas of frequent wear like, crew access trails across the hull and turret roof, hatch rims, fuel caps,etc to simulate where the outer covering of paint has been chipped away. Do not be tempted to use a metal colour for this as that is too shiny in scale. Also before you get to bare metal you need to go through the brown-red primer and on a dark gray vehicle the little red-brown edges of the primer would be visible where the paint was worn away, so grey to metal will look odd.
Here are some good articles for you to look at:
http://missing-lynx.com/rareworld.htm
Here is a link to my web site. This is of a German sdkfz 222 that I built using this process:
http://www.geocities.com/petbat1961/sdkfz222_01.html?1075352018453
As you have said, everyone has their own ideas. You may want to try the various methods before you find one that suits your style. This is all part of the hobby, trying something new each time. Just be prepared to mess a few up during the learning process- we have all been there and done that.