Here's how I did it:
Using two controllers (with a second profile logged in), I started an Annex match on Raven Down, 3 rounds with 180 points per round. I chose Raven Down because it is a small map with only two objectives.
Once the match started, I used my second profile (logged in as a Locust, though it doesn't matter which side you choose) to capture the nearest point (sometimes it will spawn right next to one). As soon as the countdown from 60 began, I ran the Locust to the next objective and parked him next to it.
I then used my primary profile (the one needing the achievement) to run over and stand next to the objective being counted down. Once the count got under 5, I crossed the barrier and captured the objective for ~5 points.
Since I left the Locust parked next to the other objective, the next countdown began almost immediately. Once again, when the countdown from 60 started, I ran the Locust back to the other objective. This saves some time, as you have to wait for the countdown to end no matter what, so you might as well set up the next capture.
After a couple of rounds, the Locust was at 175 (or so) points. I then moved him safely out of the way and captured points with my primary profile until I reached 180 total points, winning by 5 (or less). Total time for each 3 round session: about 22 minutes, give or take. Repeat 20 times (can be tedious, so I used my MP3 player to help ease the boredom), and achievement unlocked.
Hope this helps. Send me a PM/Message through Live for more information.
EDIT 8/5/19: Please see DragonYen’s comment about making this a little easier with a lower score and less movement. I’d type it out, but it’s pretty involved. Suffice it to say it’s a good addition.