If there is a software, ideally not too complex and with a limited number of features, that you maintain or just care about and that doesn't have any manual page yet, start writing a manual page for it using the mdoc(7)
Be careful to not get lost in details.
Start by setting up the preamble and all
required section titles.
In each section, take rough notes which material will need to be covered in that section. Only after that, start filling in individual sections.
Pay particular attention to get the beginning of the DESCRIPTION concise and clear. It should clearly state the purpose of the software and not be wordy.
When drafting lists, first figure out which list entries will be needed, only then start filling them in.
If there is more material to cover than you can finish during the tutorial, don't fear leaving blanks in the middle. Try to work on as many different parts as possible and take advantage of the chance to ask questions that arise.
Consider submitting the result to the software maintainer for inclusion, possibly after finishing it at home if time is insufficient during the tutorial.