Didn't work for much time, just edited the surface for smoothness. Check out the following:
The surface under the car and the wheels. Just extruded the edges from the side and then connected/capped the two giant circles to cover up behind the wheels. Then I simply extruded those edges again to cover the area under the car.
From the back, you will observe the curvature of the lower surface. That's just to cover the curved surface behind the rear bumper.
Side Skirts Vents:
After applying the detailing for the door, I realized I missed them. It took a little long and finally got the shape; Although they are longer than in the original car.