The quickest way to do this is to play solo survival on the map Cornerstone (1st level). There is a base turret right at your spawn. You should rack up a few hundred kills in just two or three tries. Just play through until you get to wave 4 (which will have two hectors). They will probably kill you and then you can just hit "Y" to restart. This will restart you at wave 1. Just do the first 3 to 4 waves killing as much bugs as you can until it pops.