The trick for me was to do it in burst. I would have never gotten it down going all at once past like the number 200 or so and it’s draining, especially when you know the words but are just trying to get the reviews over with.
My strategy when I get behind is to just do enough every day that my 7am hour (when I typically do my first review session of the day) count for tomorrow will be lower than today today’s 7am hour count. e.g. tread water and slowly work the pile down.