A simple and effective way to get this is to allow a titan to grab you, then break free of his grasp and fly around in his line of sight, hoping he makes another attempt to grab you so focus time kicks in.
After you break free, you'll notice that you'll have a teal colored bar underneath the bar for your blade durability. That's the number of times you'll be able to go into focus time (I believe it's 2 times), and from what I experienced, it happens at random. When he goes to grab you the screen will go blue and everything will be in slow motion. That's when you boost in any direction to avoid his hand. Do this 30 times and the achievement is yours. This can be done in any game mode.