I'm sure you'll find the answer in the thread that's been linked...but I wanted to say a few things...
* You may find the reflection of your windshield may block the actors. Depending on the angle of the windshield and the angle of the sun.
* The DP can get on the hood and shoot through if you are able to travel at a safe speed, on a safe road.
* You can substitute a profile two-shot from both sides for your frontal two shot.
* Using a small bar light below the actors works well for night shots.
* If you have a sunroof, you can sometimes get coverage through that.
* If you have an SUV or truck that has side steps, or whatever that's called, you can have a DP stand outside the moving vehicle on that and shoot through the windows.
* A car traveling next to you sometimes works well.
* Bad green screen is bad...
* You can poor mans the whole process (if at night) by shooting in a dark garage. Light the interior...and from time to time have some one move a light past the actors faces and the car. You can also add street lights and smaller details in After Effects if you know how. You can also have someone slowly rock the car from the back to simulate natural movement. Just don't make it too obviously a rocking...
Those are just a few tips from an indie perspective...