Instead of waiting till the final draft to tackle the dreaded task, I started writing a summary as I finished each chapter. But I didn't begin to do this until I was more than half way through the first draft, so I had to catch myself up, reviewing and writing summaries for all the chapters up to that point.
The first good thing about it was the way it ended my confusion about what was happening at particular points in the story. That's why I did it. I was lost.
The second, unexpected good thing was how the summaries showed problems, contradictions, and inconsistencies. I found chapters where there was nothing much happening, or too much. Plot threads I'd forgotten about and hadn't carried forward.
I still hate this kind of writing, but heartily recommend you write summaries as you go along. It's easier when everything's fresh. Use the summaries as a reference to keep yourself straight. When you write the next draft, revise them as necessary. When someday a publisher asks to see your first fifty pages and your chapter summaries, the summaries will be seasoned veterans.