Like it has been said before the best route to take is the "rolling thunder" event. However, if you don't want to spend 2+ hours mindlessly blowing things up, you can do what I did and tape/rubberband your left stick to the left and your right trigger down so that your tank just keeps autofiring and turning. I managed an average of more than 1000+ kills each time.
Don't worry about hunters as your tank will be able to handle itself, all you have to do is hit the X button to restart every time the event ends and you can be lazy like me.