It's a good practice to have your code internationalized. The coding pattern for doing so in NetBeans modules is following:

org.openide.util.NbBundle.getMessage(FindResultsPanel.class, "FindResultsPanel.btnModify.text")

Here the FindResultsPanel is the class where the text is used, The Bundle.properties file resides in the same package as the class and the getMessage method makes sure it loads properly in an efficient manner. If you are coding a NetBeans module, you should avoid calling java.util.ResourceBundle directly.

However it's been always a pain to edit the text. First you ned to find the I18N token, then find and open the relevant Bundle.properties file and then find the line with the I18N token. The pain has become unbearable for me and I created a simple module that's capable of "hyperlinking" to the correct location in the correct resource bundle file directly from the java source file.

The hyperlink is invoked by pressing Ctrl while pointing to the I18N string. If you wait a bit, a tooltip shows with the actual message text from bundle file.

The module NBM file can be downloaded from here.
Works in Netbeans module projects only (both Ant and Maven based)
It will eventually make it either into the Maven support or the NetBeans module development modules

Enjoy.