Hi Rudl - just in general when you have a shape that is more kind of blobby and without distinct edges it can be easier to build such things in a poly modeler rather than in a NURBS modeler.
That's because the main strength of a NURBS modeler is in being able to create shapes from 2D profile elements quickly. When your shape does not have distinct edges it means that you are no longer operating in this area where NURBS modeling has its greatest strength.
But if you do want to try it in MoI, you would generally approach it in the same way as lyes' tutorial, you need to break the car down into some panels and work on creating some of those panels. For smooth areas you may need to do something like put in some blends to make a smooth connection between 2 panels.
It tends to be a much more advanced area of modeling, it may be something that will take quite a lot of practice and experience to handle well so it may be difficult to get a whole lot of help with it here.
Here are a few other links that you can study which may help though:
