When time is short, you can save yourself quite a bit of time by never breaking off the unused ends of balloons. Most of the time when using the techniques described here, you're making closed objects. Simply make sure that the tail ends of balloons are stuffed inside the sculpture.
Likewise, it's often faster to twist new balloons into sculptures rather than always tying nozzles on. again, just make sure those loose bubbles are found inside.
Sometimes when working fast, bubbles end up not being as regular as you'd like and you can't quite get the shape you're trying to make. Rather than slowing down, you can often make corrections for your errors by filling the inside of a sculpture with round balloons, or possibly even other objects that have the shape you want.