There is a scheduled action in the /system/webdesign.pma application that runs daily at 4:00am (called RefreshDesign, source included).
To use the templating feature, in the application settings section of the application to be the TEMPLATE. Put a unique name in the "Is a template:" field eg "Cannibal2". Next open the app settings of the application to inherit from the template and in the field marked "Inherited from:" put the same value eg "Cannibal2".
If you wish to force a design refresh, simply tell the agenda task (through the server console or programmatically) to run the action now:
tell agenda run /system/webdesign.pma/RefreshDesign
Using templates is a very powerful feature. On this site we run about 5 instances of our content management system (Cannibal) which allows us to make a single design change and have that reflected in all application instances.
We acknowledge that a remote design refresh would be very handy and are currently thinking about the best way to achieve that. SOAP and XML over http seems like a good solution but there are a number of complexities.