If you want to create a new language pack for v2.72, simply follow the directions posted in this thread: http://paintdotnet.12.forumer.com/viewtopic.php?t=601
However, for all the authors of the v2.6x (and earlier) language packs, you will want to make use of a program such as WinMerge ( http://winmerge.org/ ) to compare the English Strings.resx files from v2.5/v2.6x and v2.7x. This is known as a "diff" utility that is very useful in highlighting the differences between two text files.
Basically you'll need to download the source code for both the original version for the translation (v2.5 - v2.64) and v2.72, and then load up the src/Strings/Strings.resx file from both in WinMerge. Lines of text that show up as yellow are new, and lines in red are to be deleted.
Make sure that your Files.AboutCredits.rtf is up to date as well. The changes are minor, and mostly involve removal of some items in the "External Libraries and Contributors" section.
Once you have updated your language pack, simply post it as usual in The Official PdN Localization Topic over here: http://paintdotnet.12.forumer.com/viewtopic.php?t=486
Thanks!