I built my setup some time ago, but the other day someone on the net mentioned using a tuba mouthpiece. Not a bad idea. Also, people have said they used aluminum foil with holes poked in it. The point is to get a lot of burning done without using an overly large volume of air. Do not however, deprive yourself of too much oxygen.
Some people like to push the bottle to the bottom, and then inhale.
If you try this, don't displace so much water that the bucket overflows. If it is your first time trying the system, do some trial runs without packing the bowl and lighting it. Any other tradmarks, trade names, service marks, or service names used on this site are the property of their respective owners.