1. Drybrush: Take an old artist's flat brush (or even a filbert will work), and dip the tip into the color you plan to drybrush. Next, work the paint out of the brush with an old rag or paper towel; use back and forth strokes. When all the paint is off the brush, slowly and lightly brush back and forth acros the raised surface areas you wish to highlight. The remaining "dry" paint left in the brush will begin to deposit on the surface. The more you drybrush, the greater the deposit on the surface.
2. Washes: These should be done prior to dry-bushing. Washes are nothing more than a little paint (couple of drops) and a lot of thinner. They can be any paint (enamels, acrylics, oils, etc.) and their associated thinners; paints also need to be compatible. A wash should be the consistency of coffee (?!) when applied. I personally prefer a fine liner or 10/0-type brush to apply the wash. Take the brush, swirl it in your mixture, take off just a little paint, and then touch the brush at the join where the vertical surface meets the horizontal. Capillary action will pull the wash around all the corners and into cracks, etc. Washes can also be applied over the entire model to vary shades in the overall vehicle color (I'm primarily an armor modeler). Some modelers, among them Paul Boyer of FSM "fame" recommends coating the model with Future prior to applying a wash. He uses this almost exclusively on aircraft as part of his "sludge" technique (see p. 81, July 2003 FSM, and Nov 2001 FSM).
The important thing to do is experiment on a couple of old kits until you get results that YOU like. This hobby is its own art form: Have fun!
Gip Winecoff