What you could try in the bubbled places is to slice around the bubble with a utility knife, and then coat over the top with some skimmed off coats of all purpose drywall compound. Use a wide taping knife and keep the coats thin. After each coat dries, scrape off any bumps or ridges with the edge of your taping knife before recoating. Feather out the edges, lightly sand, and when all done prime and paint.
If your bubbling is excessive and your seams and corners are all messed up, then the only fix is to tear all the drywall off and reinstall, but that turns into a big job.