i used to do fiberglass , and if i had a bubble , i would put some epoxy in a syringe (its not eaasy , as the epoxy is thick), squirt a little under the bubble , then work it around and squish it out the needle hole. such a tiny amount was needed is done right , it almost seemed like too much work.
then again my glass was holding couple hundred pounds of a/v equip , and was also pressurized when the woofers were on...