I can only agree with what I read in the prior suggestion, but would like to add the following: Try not to make your tank look rusty. Rust on an operational tank is rare, with a couple of exceptions. The first one, of course, are the tracks. End connectors will rust overnight on an operational vehicle. The second biggie is the lower bow plate, it takes A LOT of abuse. The third exception, which almost everyone ignores, is bullet strikes. If you look at old pictures of WWII tanks, you will notice that many of them are covered with "freckles". These are bullet strikes on the armor. Small arms fire won't even dent the armor on a tank, but it will chip the paint off. After awhile, the bare metal will oxidize and form a dark reddish brown patina at that spot. If you want a "combat vet", don't forget the freckles. The best way to apply freckles is to take the darkest brown you have and mix in a little black to make it even darker. Then dip the tip of a round pointed toothpick into the mixture, tap it once on a different surface than the model to get rid of excess, then tap the tip of the toothpick over the surface of the model so that little dark spots appear. This should be the last thing you do to the vehicle, otherwise they might disappear under your drybrushing and pastels. Have fun detailing.