I know the feeling. A lot of the exciting stuff has been done and you feel like you're kinda left with the boring bits.
I started keeping detailed notes while I'm still in the thick of things, and that helps a little—feels like I'm already part way there before I've even started. It's a fine balance between getting an extra edge on the insights while in the moment, and joining dots that don't actually exist, so some care is needed.
Documenting summaries of findings in Keynote with scribbles and annotations and screen examples and the occasional chart keeps it tight and the focus on communicating what we learnt and how we evolved the design.
Doubling up some thinking for use in your portfolio and future discussions might also help?
But it sounds like you're needing to write up stuff in a lot of detail. As long as it's not too heavy (are people going to actually read it?), I keep wisdom from @joenatoli's Think First in mind: "No documentation means no win." Just repeat over and over before you go mad with something else.