The gist is of the utility is this:
You fill in a table specifying the custom buttons you want and which tabs you want them on. Then the utility automatically builds the custom XML and adds it to a new workbook or existing workbook, effectively applying your Ribbon customizations without writing one line of code.
I've also made it so that the call-back functions are also created and added, so the buttons work right away! The source code is open for anyone who wants to build on this and create a better table-driven Ribbon Customizer.