Definitely recommend externalizing your strings into one of the standard localization file formats (.po, .strings, XLIFF etc.) as mtmail suggested.
Once your content is in a file, you'll be able to use a platform like Transifex (disclosure: I work there) to manage and automate your localization process. You'll be able to invite your translators, track the progress of work, and communicate directly with them. Once the translations are done, you can get the translated files via the web UI, API, or command-line tool and use them in your apps.
Most of our customers are software companies and use Transifex to make localization manageable even with daily or weekly releases. We have a case study of Eventbrite on our site at https://www.transifex.com/customers/casestudies/eventbrite/. Disqus also talked about how they use Transifex at a conference a few years back: http://confreaks.tv/videos/kodio_2014-continuous-translation....
Hope that helps!