http://rat-look.com/forum/index.php
I'd avoid the rusty paint as it looks crap and is old hat now, there no quicker way apart from a large hammer and fire to decrease the value of the car.
Not seen many rat lupos done well tbh and the base colour will have a big factor in it. Most over do it with that bloody rusty paint. Low, real or forced patina, motorsport wheels is a good start. Take inspiration from this imp: http://rat-look.com/forum/viewtopic.php?f=10&t=8816