Best when done in single player.
By the final 2 towers, you may have difficulty hitting the buttons fast enough.
Controller: I wrap a tube of chapstick or a thick pen with a scrap of cloth (reduces friction) and rub across the buttons really fast, with a finger on the other hand ready to hit the trigger. If you fail, Don't worry you can retry and still get the achievement.
Fightstick: If you are using a fightstick, you have a better chance with fingers, but the chapstick method will not serve you here because of spacing. But because of spacing, you can get a friend to physically help you, or find a weird sturdy sheet that will hit all buttons.
Keyboard: There are many macro programs you can use to simulate pressing JKLI keys 1000x per second. Unless you are an active StarCraft player, then you can probably hit them fast enough.
BONUS! Completeing the tower will get you the Revenant Sub-Zero skin. It's very COOL looking
