Afterwards I start to trace the basic outlines of the car with splines, following the different contours. Personally I use Rhino for this, but you can do this as well in 3dsmax..



In a "few" hours you should end up with something like this:
Note that you only have to trace half of the car, since cars in most cases are symmetrical around the center.


You will not use the splines to model the car.
They will only be used as guiding lines underneath the poly mesh..