help/docs for modifying and testing translations

I'm trying to modify and test translation strings for F123, a screen 
reader friendly Linux distribution that focuses on localization and 
translations into many languages out of the box. We are using Firefox 
for browsing, and are likely to use Thunderbird as at least one option 
for e-mail. I'm looking to either pull out a few languages that 
currently don't work well with screen readers and modify them, or to 
create new translations for certain languages that need to be modified 
to make screen readers and speech synthesizers work better with them. 
This for now is being done in our own environment, as the modifications 
we make will likely not be usable by the community at large, due to the 
way the strings need to be modified to be compatible with the speech 
synthesizers. Looking at the localization tree, I see things grouped by 
languages, and then by browser, mail, etc, but it appears that there are 
various file formats, even in the same language, that all have strings 
and their translations. Is there specific documentation that I can use 
to find out how everything goes together and how to build a modified 
translation for an already packaged Firefox or Thunderbird? I am 
assuming this can be done, as both products have separate packages for 
most languages. Is there a build tool or something that takes these 
various formats and compiles them into language packs that we can 
package and install independently? Thanks for any help.

~Kyle

F123 sorftware development