Here is one way to take a simple texture and apply it to a shaped object like a car and have it appear to follow the body contours.

1. Start with you original image


2. Mask the portions you wish to exchange for your material image.


3. Duplicate the image layer and mask then invert the mask to reveal the body on the second layer. Then desaturate the body color and adjust the contrast till you get a well defined grayscale image that keeps the highlights and shadows. (The desaturation keeps the original colors from bleeding over to your material image.)


4. Insert your material image on a layer between the bottom layer (gray car body) and the top layer (the roof, wheels, etc.).


5. This is what the layers look like before you adjust the blend mode of the material layer.


6. Change the blend mode of the material layer to overlay and you get this: (Adjust the opacity and fill of the bottom gray body layer to fine tune appearance.)


7. You can add multiple material layers to try different looks:


Hope this is not too simplistic a tutorial. I have additional layers shown in the post which were used for additional materals and text added to the final image. You only need the three I indicated to get the final image shown.