Just have in mind - that some add-ons modules still have hardcoded text - and seems to have seen a thread here that the very core portion also has some hard coded text strings - but not sure.
Export the xml file including not translated phrase to your local drive. Edit the file with utf-8 encoding... And if you wish to install add-ons - then translate the install xml file before install it. Thats the easiest easiest. We also have the problems with 12 am/pm vs ours 24 H notation..
If you encounter some words you can not find, let me hear from you. Has even endured a lot with it, so there's no reason that you should suffer the same.
Thanks Walter! And greetings goes back to wonderful Austria
BlackMuddler: Thanks for the heads up, I hope the developers of both XenForo and add-ons will make adjustments so that translating everything can be made as easy as possible. Since this software reached 1.0.0 yesterday it's probably a lot of those small quirks which will be fixed in time. Btw, the xml-translation of add-ons before installation is something I've used to do when doing the same with vBulletin earlier - but thanks for the info, then I know what to do here as well. For now, anyway.
I have a good feeling about XenForo, and I think it will change the whole forum landscape over the next years. In a good way I'm already looking forward to upgrade my vBulletin forum to XenForo when the day comes that user albums also will find it's place in this software.
Started that way my self - after one day I stopped at took the text editor way. There seems to have a much better view of what is coming, it's easier to search with a text editor - also have color syntax, so I'm sure that I do not accidentally delete a  sign.
Are confident that you will come to that too. It is much better, faster, and not least easier.