It isn't only a lot easier, but it is also "impossible" to strobe a black car. Only thing you can strobe with a black car are the surfaces that are reflected in the paint. You can jack the power output on your strobe facing a black car and it will look the same as no strobe. Only the non-black surfaces will illuminate.
But with that said, there's good input here. Hot spots. You can do a lot by moving the light around and aiming it a bit better, however, without a continuous light (like in light painting) the strobe will always cause a certain degree of hotspots that will need to be tended to in post to smooth everything out. The suggestion to start at night is a good one. It will help you understand the positioning of the strobe and how it affects the outcome. 1 strobe is plenty to light a car, it will just end up being a composite image. If you want to be able to shoot a single image with everything strobed correctly you wont have the room in your trunk to carry all the equipment 
With respect to the F-stop. 2.8 is too low for just about any car shot where you see the entire vehicle. Nor is it really needed.. Sure the nice smooth, bokehlicious backgrounds are great, but not if you car is not in focus at either point. Unless im shooting from a side profile I will typically shoot no less than 4-5.6, but more around 6.3-9, it helps bring all of the details of the car in focus.
One more tip, you have a B1600, more than enough to put out some good amount of light, if you went up in shutterspeed to your max (1/200 or 1/250), lowered you iso to the min, and kicked up your f-stop it would have allowed you to kill off some of the ambient light. You then could have compensated with the strobe output and fired it a bit hotter. The result would have been a much less exposed background (to kill all the unnecessary busy detail) and a more contrasted subject, that a long with a bit of a warming filter in post would have given you an awesome looking "strobed" image. Silver cars are on the easier end to shoot, they aren't white so its kind of hard to blow-out all of the detail with overexposure, and if done right the metallic flake looks awesome with the strobe.
Remember this: With strobe photography one of the most important things to understand is the balance between ambient and artificial light. Getting the correct balance is what gives you the strobed "look" and undesrstanding how to achieve this balance with you camera settings will make it much easier to shoot.
