uni> I didn't actually know how to use it either, but follow the guide, and mine worked out first go. Basically it installs the OS X Mavericks installers to a >8GB USB disk, then patches the boot.efi using the custom serials numbers your Mac Pro has. So, when you install OS X it copies over this new boot.efi and you will never need to patch Mavericks manually (it's fine with 10.9.1 but apparently the beta of 10.9.2 does alter it, but no hassles at present)

The guide:

http://oemden.com/?page_id=585