Zombie hit the nail on the head. Just remember you can always build up more layers of paint, so it's really impossible to have too little paint on your brush. For washing, I'd also recommend that you use various colors for your washes. When I first started that, my impulse was to use black on everything, but If you do, it can make some colors look dirty. Take cues from real life shadows...you'll notice that shadows on snow almost always look bluish, not black. I use a dark brown as a wash on skin tones.
Here's a sample of something I did years ago using both washing and dry brushing:
I used different color washes on different areas. I did used a wash of green and then black on the skin so it looks mottled and ugly. I used a brown wash on the fur.
Something else to think about...if you really want your highlights to pop, do the washes first and then the dry brushing. If you want them to blend more, dry brush first. I did both on this one, too. The skin I dry brushed and then washed, and the fur I dry brushed last.
