You learn how to do Rush Attacks a few missions into the start of the game.
I'm not sure if we'll make this one but the game is still fairly new and this is a pretty easy thing to do.
I made up this image which shows the top current top 100 players on TA with Rush Attack kills and the amount of people that have unlocked the "Don't Hit the Brakes" achievement. I will monitor these numbers and update them every few days to give us all some idea of the progress that we're making. Obviously I can't account for people that don't have their gamertags registered to this site which could be a good thing as maybe someone who is obsessed with Transformers is playing this non-stop and racking up RA's.
Here's the image:http://postimg.org/image/fabkfpsxt/
I don't think any grinding will be needed but obviously any stages with a lot of weak enemies would be the ideal place to do so.
I will repeat this from the last T:D community challenge solution for any potential newcomers:
In order to make sure you get credit for this challenge simply kill a single enemy with a Rush Attack and check to see you got some percentage in the "Don't Hit the Brakes" achievement either on the Achievement app on the console or the games page here on TA.
The challenge should unlock for everyone a couple days or so after the challenge time expires if the goal is met.
Update 1: Been roughly three days and I already see about 1,000 RA's accumulated among the top 100 on the TA leaderboards.
Assuming this amount keeps up that should be somewhere over 4,000 just based on top players alone. I'm not accounting the other 1,400+ players tracked on this site and the people not even on this site but factor those in and we should reach the goal.