Use your second controller to sign into another account before you hit public match. While in the public match, you can hit circle to back out the second controller right before the game starts after readying up, which allows you to play with three or two people. Make sure you don't sign in as a guest with the second player, it HAS to be another account. If not, then you'll back out both your main account and your guest at the same time, and you won't start the game.