Hi, Andy.
In regards to washes, take a few drops of black paint, and mix it with a lot of thinner. You'll have to stir frequently to keep the pigment from settling. Then take a fine brush (I personally like liners for this), dip it in the mix and then touch it to a crack or corner of raised detail that you wish to highlight. Capillary action will draw the wash around over and through the detail. After you have applied your wash, then lightly drybrush the raised surfaces, and watch your tank come alive with detail. Personally, I like to use dark washes (black, etc.) on dark painted vehicles, and raw umber, burnt sienna, etc. on tanks that have a light or desert paint scheme.
Drybrushing is really easy. Take a lighter color than what your base coat is. You can use the base color + white, or use colors like armor sand, or one of my favorites, radome tan. Get an old flat brush, dip it in the straight paint, then remove it, and using an old rag or a paper towel, brush out the paint until there's hardly any left, then LIGHTLY hit the high points on your kit using a back and forth stroking motion with the brush. The more you brush, the more dried paint you'll see deposited on the detail. If you need more paint, simply repeat the steps above. Of course, colors can be varied, depending on the effect you are trying to establish.
Make sure you practice a little first on an old kit or piece of plastic, and then go to it.
Hope this helps some.
Gip Winecoff