I doubted that this could possibly work, but I was wrong and ***it 100% worked***! The hinge on my MacBook Pro 15" (2015 version) very quickly started to show resistance over two days about a week ago, and it's been rough ever since. It required a worrying amount of force to open and close, and it refused to stay completely closed, basically bouncing back open with about a 0.5cm gap in the front. I assumed I had somehow accidentally bent the frame and that it was not salvageable. Wrong!
I followed @danj 's instructions above, and my MacBook Pro's hinge is as good as new! I took a few photos while I had the bottom panel off in case it might help other people because the picture with "oil here" label appears to be from the screen's side, not from the bottom's side (with the logic board). Here is where I applied WD-40 with a Qtip, and I also took some time to carefully clean any dust and grime that had built up inside the case.
Thank you very much for this solution, @danj ! 🙂
(Posting as a second answer only because I can't include this image as a comment on the previous answer.)
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