First thing to do is to snap the achievement onto your screen to monitor if you go over the 60 seconds allowed. (You will know this has happened if the progress bar resets to 0% and you will have to begin back at the 1st Shotgun Universe screen and start again.)
Then start the Shotgun Universe set of levels as shown in my video but if you die or think you've taken too long on a particular screen just hit the
before entering the portal. This will take you back to that start of that screen but will also reset your time back to what it was when you first entered that particular screen basically giving you an infinite amount of retries to perfect the screen.
You do have to make sure you do not go over 60 seconds however as this resets the achievement progress bar which the
button trick cannot rectify so a rough mental not needs to be kept of how long you've taken each screen.