“bubble bubble toil and trouble”
Very early in my fusing experience I researched bubbles and gave up because there are quite a few things that cause or assist in making them. Some of which are: shelf not dried out from wash; uneven distribution of glass causing relative ‘weak’ spots where there is less glass; and firing schedules to name a few.
The shelf side of glass will always be textured or matt no matter how smooth you try to make the shelf. So why not just go with it. Fire on top of a thin fire matterial or other shelf type papers or fiber products. You will never get bubbles since air will escape via the shelf lining, and learn to love the various texture possibilities you can come up with by using all sorts of fiber based products and doing things with or on the fiber/paper.
As far as saving the piece that has a raised bubble. You can put it back in the kiln and raise the piece to bending temp. Use a stainless steel soup ladle or some such tool to push it down by rolling the ladle over the bubble, then follow a regular schedule to bring the temp down to room temp.
Since your a newbie I need to tell you to turn the kiln off when reaching into it and use a kevlar glove or some such. After you pushed it down, then turn the kiln back on and continue with the down ramp part of the schedule.