Alana is right, I do use a dental vibrator. It's the larger rectangular one. I wrap it completely in plastic wrap before I use it. I place the mold on top and slowly increase the vibration. I find that this helps the bubbles work their way up. I don't usually leave on tray on while I fill another because sometimes they bounce right off. They can move around quite a bit. Often, I tuck my pinky up into the corner of the mold so that it can bounce a bunch but doesn't fall off.