The two images don't really have the same effect, but I can see what you are coming from.
They both use a combination of natural environment lighting and added softbox/diffused photo lighting. This causes the look of the bodywork appearing reflective in some areas and almost matte in others. The natural environment is providing the sharp reflections and use of large softboxes adds the large areas of soft light mainly along the sides to express the subtle curvature.
In the first image the windows on the opposite side of the roof give long streaking highlights along the roofline and tail of the car, while soft diffuse panels at ceiling level add the soft light to the near side of the car. Also the whit panels on the floor add important highlights the bottom portion of the bodywork, separating the car from its surroundings.
The second image seems to have one large square softbox directly in front of the car, slightly raised to catch highlight on the roof, and two narrower sorfboxes side by side along the flank of the car just above the level of the camera. The building behind causes the darker shawow areas over the bonnet and sides of the roofline. The light from the sky of this outdoor environment fills in some areas in-between the shadows and highlights and the trees add some natural detail in the reflections.
For the materials i would definitely start with the metallic paint material with some roughness on the metal colour and perfectly clear top coat and no metal flake visibility.
To create the environment you can start with a suitable real life outdoor (or indoor with plenty of natural daylight through windows) HDRI as the base, and either add light emitting planes with the keyshot emitter materials or use a packing like HDRI Light Studio to add light panes to your base environment.
Also I would say that for this type of image I find getting 70/80% there in the render alone to be quite acceptable, some post work is to be expected. Many photographers doing car shoots would take several images with different light setups to bring out key details of the bodywork and then combine those exposures in post to have full control over the final result.
One note for some added realism, especially when the subject is a classic car like in these examples is that the bodywork was probably hand built and therefore not always perfectly straight and smooth. Note for example the highlits along the doors of the second image, how it has a slight wobble. You can either incorporate this into your model/mesh, or use warp tools in post.
Hope this helps in achieving your desired look.
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