Great. Sounds simple enough, but now how does one "Create a data property data format" to which to point my property set?
Open the Style Manager. Under the Documentation Objects node, you will find a Property Data Formats node, with the Property Data Formats that are defined in your drawing listed underneath. You can create a new one from scratch, or, if there is one that is close, you can copy it, and then rename/edit the copy to suit your needs. You would then need to use the Style Manager to copy the Property Data Format to any other drawings that need it. (Copying a Property Set Definition that references the Property Data Format will bring the Property Data Format along for the ride, as well.)
Beautiful. Thanks for pointing me in the right direction. Problem solved.