Automatically populating the Directory key on Polycom phones (and Cisco)

I am currently using the FreePBX distro primarily with Polycom phones. These phones have a directory key on them but it is currently empty.

In end point manager there is 000000000000-directory.xml which is currently at the defult

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

The end result I would like is that when a user presses the directory key it shows all of the extensions that are defined. I would like if possible for this to be automatic or dynamic in the sense that when an extension is added it updates the directory on the phone.

I have done some Googling but have not come to a good solution yet. We also have Cisco 7940 phones that I would like to have the same functionality.

I just found this but hopefully there is an easier way as this is above my head at the moment.