I just finished replacing my Mac Book Pro Retina Mid 2012 battery after reading through these instructions and comments. I ended up using the string technique described and shown in a YouTube Video. I was able to removed the batteries in about 30 minutes taking my time and being super careful not to damage anything else. I then used a roll on Tea Tree oil to dissolve the remaining adhesive and clean up the battery container area. It worked well but took me another 45 minutes. New battery installed in less than 5 minutes once all that was clean and dry.