I'm back again

First can i say there are loads of really cool models on this web site , i only wish i could produce the same

In an attempt to do so im after some help on were to go next with this model.
I made a start but now im not sure what to do next.
I have tried washing it and using pigments ,with a variety of success.
I'm now using a airbrush to apply the paint and what a difference it makes.
But any advice would be cool. As im not yet finished the model

I forgot to ask , How do you do the windscreen effect that makes it look like the wipers have made a clean patch on the screen?