1933 Chevy 5 window coupe

This is the current place on the work on the 33 Chevy. As you might see there is still several areas that need finishing. The intersection of the compound curve areas need to be solved as well as other intersections of the model. Again I am looking for input on how these problems might be solved. I have solved similar problems on the Airstream work. In the Airstream projects I solved these problems by drawing in 3D a single point and line at a time. Similar to what one might do if they were working in Maya or other 3d software. My challenge here is to find ways to solve these type of drawing problems in SketchUp using SketchUp tools. All suggestions and or examples would be appreciated.