Basically if you want to build a model using a method of shaping one small area at at a time out of a larger smooth surface, then you should be using sub-d smoothing in a polygon modeler for that type of an approach rather than trying to do that with a NURBS modeler.

The strengths of a NURBS modeler are when you create large sections of your model out of curves that you draw, with some curves making broad extended shapes and other curves slicing away some parts of that broader shape to make holes and more irregular outlines.

If you are not able to model with that kind of an approach then it usually means that your project is better suited for a poly modeler and you're going to be struggling a lot trying to do it in NURBS since you are trying to use a different workflow than the one that is most suited for NURBS modeling.

- Michael