Mass Effect Legendary Edition

If you’re not playing as the appropriate class to bash this out nice and early, I’d recommend waiting until you’ve finished the Citadel DLC and have access to the combat simulator.

Once in there choose EDI and Garrus as they both have overload. Select Geth Elites as the enemy, (this is unlocked with silver tokens) as all of the enemy’s you’ll face will have a shield active.

Set the difficulty down to narrative and turn off the ability for your squad mates to use abilities unless you say so.

Now jump in and have EDI and Garrus cast overload until this is boxed off.

It took me about 15 minutes to complete

I can guarantee that you can do with squadmates. As I've just done it with Garrus and Kaidan (you can use EDI if you don't have Kaidan).

An easy way to do is on the mission "Arrae: Ex-Cerberus Scientists", right at the start there's an auto-save, you walk about 30 meters and there's Cerberus Operatives falling down on a Generator that provides shields. Up the difficulty to a level where they don't die from a single overload and you can keep farming the same guys. When they all die, the game does not auto-save, so you can load the previous save game and keep doing it until it's finished. Done in about 10 minutes.


EDIT:
Just added a video with these details: