I parked my car in the garage at night with all lights off so it was pitch black.
Basically I set my camera to 13 second exposure, 5.6f and ISO 100.
I took an LED flashlight and very briefly lit up different portions of the car on each exposure. It's actually pretty simple, just takes some trial and error on how much light you should use in that 13 seconds ( I used about 2 seconds of light on and the rest off for each exposure.)
I then took the best 3 images and edited them in Adobe Lightroom, white balance, boosted contrast, sharpened etc.
Then I took all three images into Adobe Photoshop and blended them together for the final image.
Here is a link with the original 3 pictures so you can see kind of how I blended them.