Well Brock is still very young, 15 weeks on Wednesday. I tried the 'look at me' along with treats and he did very well. Even worked on some basic commands and he kept his focus on me. He's extremely food motivated (almost to a fault lol) so if I have treats his eyes are on me!
"Look at me" is a good way to start, but it won't help him when you are not present, nor when you don't have treats on you.
If you want to create a different response to cars - being aware of them, not interested in chasing, not triggered by them, etc. - you will eventually need to move past "look at me". This is possible to do using treats or other reinforcers (and that is my own choice when creating a good awareness of cars, while teaching the dog to stay in his or her right mind around them), but it does mean eventually building on the foundation that you are setting now.