Using a script similar to the one below, I was able to quickly update over 700 Chromebook devices in a Google Apps domain. I had a spreadsheet with the device's serial number and three columns of information that needed to be added or updated on each device. The spreadsheet was saved in CSV format and looked similar to the text below.
* Update March 2016:
There are much easier ways of accomplishing this task now that GAM can query Chrome device serial numbers. Maybe I'll update this post with a better solution at a later date.
GAM Documentation: https://github.com/jay0lee/GAM/wiki
GAM OAuth Instructions: https://github.com/jay0lee/GAM/wiki/CreatingClientSecretsFile