For end users
How do I brief variables in a Branded Template?
It's best practice to put all the template's static elements in the InDesign file's static layer and put all the different variables in the variable layer.
Sharing an example PDF with sticky notes together with the InDesign package is a must. This helps us to understand all the dynamic elements of the template directly.
In the PDF, you can explain certain business rules like the maximum amount of lines/characters of text frames, possible naming of image switches in the filter, and the naming of general filter fields.