Player 2 : Jump into the 'infinite portal' like a good player.
Player 1 : Now on the first horizontal panel to your left (near the ground), set your EXIT portal and watch as player 2 zips up high into the air.
Player 2 : As you reach the switch (either on the way up or on the way down), press the action button.
Player 2 : You should find yourself sailing up the other side of the wall as soon as you've pressed the other button up near the top, you'll release the weight ball.
Now drop it in its required are and the exit will open up.