What is the best way to paint Warhammer models?

I was just wondering, is it best to put them together then paint them, or should I paint the individual pieces and then put them together?What is the best way to paint Warhammer models?
I like to base coat them first then I put them together then I paint the individual colors. It just works better for me that way. When I paint them all the way first I tend to not fit together as well as they could, and if I glue them first I sometimes miss parts and have the grey spots. I use a spray primer though so that might make a difference too.What is the best way to paint Warhammer models?
It depends on the model, it's hard to paint behind a Space Marine jetpack so I would leave that part off until the painting is finished.