How to update a language module

Hello,

I have managed to create a language module using the tutorial found here. It's actually just a cloned of the English module as I wanted to have the English (US) with the US Flag instead of the GB Flag in the languge switcher. I have uploaded it to the server through ftp and installed it from the Studio. Everything works fine.

I didn't do the Packaging step because I won't publish the module in the market as I will be using it for your own needs.

Now my question is: How to easly and safely update the created 'English (US)' module when a new version of UNA is released and when there is a need to add/remove or change some language keys?

Should I necessarily need to create an upgrade script/app for the language module?  or is there any other way to manually update the language module through ftp?

Thanks