I had the same problem, spend a few dollars on sand paper going from 40-80-180-220 you can get the kind that have a sticky back and attach to a wheel for your drill ( made by 3m)
sand it with the 4 to get er down to bare metal, then feather out the edges and sand your main area progressivly finer, use a self etching primer then i like to use a sandable primer, sand it wet 400-800 to make it blend with the original paint still there. then touch up paint if you can get it.
at least that what I did... without the touchup paint, becuase they dont make it and im repainting the whole car because of rust.
with the decklid lip look on the inside too, for it to bubble like that there has to be a source, mine was rusted inside, bubble outside exact same spot you described.
