Georgieboy, washing in general is a waterdown paint mixture. Black is also not your only resort. I see the your body is base coated a flesh color. Try using a burnt umber wash with a little bit of the base paint you used. Mix it real good and work in small sections. The key is not really to cover the whole figure in the wash. Try to focus on the muscle areas first and then and to your liking. If you want a great reference to learn how to paint, David Fisher DVDs all the way, or the best is to ask some of the other model artist on here. We have a lot. I really have to get off my lazy ass and start posting my recent paint ups in progress. I was also going to do a break down on dry brushing, and washing. I'll work on that soon. Feel free to PM me anytime.
J