I always wanted to do the following with radar too, but that would be nowhere near as easy. This probably belongs in the laser section, but it did not seem to fit any of those categories
The next car I buy, its laser reflection signature will play a role in the purchase decision.
The plan requires the following:
A laser source.
A Gen 2 or Gen 3 night vision device.
with those two items it should be relatively simple to get a good visual image of the laser reflection from various cars, paints, and/or countermeasures. Ideally, the testing would be done at night, inside a garage, with the lights turned off. But you probably could get reasonable info just walking through a dealers lot at night.
Hooked up to a video or still camera, it would make for a nice webpage.