Having a good underwater pullout is essential to success in breaststroke. This is especially true in short-course pools, where the pullout can account for 20% to 50% of your race, depending on how skilled you are under water. So it makes sense to work on this aspect of your race. One of the oldest stand-by drills to help with this is the Double Underwater Pull (the DUP).
With the DUP, one thing to remember is that you're breaking the rules. The rule in breaststroke is that you get one pull down and one kick before you surface and start swimming. In the DUP, you add a second pull and kick before you surface. Use the DUP just for building your skills -- not for racing!