The 6D is a pretty limited camera as far as Raw recording because of the SD card. I doubt you'll find many resources from users on it. Documentaries require a lot of recording time and unfortunately, the 6D does not have the hardware for long-duration recording.
Using a full frame 1x crop resolution at 16:9 (1824x1026) will get you 19 seconds of RAW recording.
But you can almost continuously at 2.35:1 and upscale the footage like this guy did (which turned out quite well in my opinion).
If you need help setting it up, I would recommend
ZEEK's tutorial on the 5D mark 2. I know it isn't the same camera, but it should give you a headstart. At 5:05 in that video I would change your Aspect Ratio to 2.35:1 or something less taxing and turn your bit-depth to 10bit.
You can use
RAW calculator to remove the amount of experimenting that you'll have to do in knowing your record time.
If you are open to upscaling, Topaz Video AI can save you in resolution. The 6D can record 16:9 with 1536x864 continuously in 10bit, which could be upscaled to 1080p easily, all while keeping the amazing flexibility of working with a RAW file.
Hope this helped at all.
