Despite being skill level 36, I was able to get this achievement relatively easily on the map Narrows, with the game type Crazy King. There are plenty of plasma 'nades lying around, and the map is relatively close quarter with relatively few large open areas (the notable exceptions being the top of the bridge, and the area underneath it where the rocket launcher spawns. Anyway, try to avoid said open areas (unless a hill spawns there, but be careful), and use the grav lift to get from one side of the map of the other. Try and find people fighting it out for the hill, or wandering around in the small, narrow, enclosed areas. If the people are 'pros,' then they will definitely be jumping out of the way, so make sure your 'nades count. If you run out of 'nades, then try and get out of the combat and find some more. Respawn time is time wasted that you could be using to get grenade sticks.