I did a repair to badly bubbled Slingerland interior ply recently.. There was no crack so no way to get the glue in. Rather than drill holes I cut through the bubbles across the grain and then made several cuts from that first cut back along and with the grain using a Stanley knife. This enabled me to gently peel back the individual cuts and pump in lots of wood glue without any special syringe or applicator.
I then clamped back to shape and let it set for a few days. I later dribbled a good dose of "Super Glue" in and around each of the cuts I'd made, before using wood filler and fine sanding to level the surface.
At this point I have used a paint primer on the complete interior but am still looking for that chocolate milk colour match.
Cheers
John