I typically use Krylon Grey Primer to do everything, then paint with Foundation paints as a base (in your case, I'd use Orkhide Shade for the hull and Dheneb Stone for the underside, maybe drybrush the dheneb with Skull White), but if you want to save a bit of time, grab yourself some Army Painter colored primer in the "Angel Green" color. It takes paint like a champ. You can partially assemble the model and paint the green parts with the green spray paint, and do the rest in white spray primer.
http://usshop.thearmypainter.com/products.php?ProductGroupId=2
It's all going to depend on how much work you want to put into the model. Try out a couple of test models and go with what works best for you.