@CaribenxMarciaX here is what the task will take, if it will help you nail down what tasks someone will need to do:

you don't necessarily have to find someone who knows captioning. you're just looking for a script that you can feed into a caption program as a text file

all you need is a screener of your documentary that has the time stamp running over top of the video so the person writing the captions can time them properly using an AV