There was nothing much I did really to achieve this. I renamed the folder (i.e. rt_firenzie to firenzie_s2) then compressed (zipped) it and lastly installed like a new template to J!.
I tried this with Firenzie by splitting the template by style; so I have rt_firenzie_s1 to s4 and assigned it to a menu item.
Because I don't need the other files in each template version I have to remove all the other style specific just to save on disk space and removed all entries from the xml file that reference to all the remove files like images and css specific to the removed style.
Zipped all the new versions and installed to J!.
One thing to note though, make sure you search for the hard coded template name in the index.php and css files.
Hope this help. It is quite painful with other templates.