just performed this fix and it took less than hour. skipped most of the steps, just doing 1-5 and 46-49.
after CAREFULLY removing trackpad ribbon (46-49) all you need to do is apply solvent and wait 5mins, then reapply solvent and wait another few minutes. from there you don’t even need string; just wedge the card tool and slowly work it under the batteries at the far edges, and proceed to center. that’s it. just make sure your solvent really has the time to saturate the old adhesive. also, running the battery down will help keep the area warm which definitely helps with getting things loosened up.
hope that helps. great tutorial and as usual, excellent product from ifixit.