1. I'm assuming youre talking about ww2 german armor. I think early in the war tanks were gray based, then dark yellow, red oxide, and also dark green. I dont know which order red and green went. I usually dont look up paint schemes because im still new to armor and dont like insane accuracy.
2. Dry brushing is to make details more visible. Most people use the base coat lightened with white. You can also use a metal color to show paint worn down to the steel. You dip your brush into the color you want to use and then wipe it off on a towel. Check the brush by brushing a piece of paper or something. If any paint comes off, wipe the brush with the towel again. When no paint comes off, then you can brush it on your model. Remember to experiment. Words can only go so far... Go to www.missing-lynx.com. The people arent as friendly as the people here, but the articles are very useful.
Oh yea, welcome to the fsm forum.