Dear kperison, I have a few suggestions for you.
First, paint the background, which should not be too detailed since it is set at such a distance away from the viewer. Remember, you want to create an illusion of depth and distance. Use the "vanishing point" method.
To create transparency, you could add a medium to your acrylic paints. Also, you could add just plain old water. The point is to dilute the thickness of the paint. In order to acheive the transparent look, you need not add more than one or two coats of diluted paint. If you have any more questions, I'd be glad to answer them. Thanks.
D. Windseth