Add custom buttons to TinyMCE

Hey!

I'm using the WYSIWYG API with the TinyMCE Editor to also allow less technical users to contribute to my wiki.

Of course, a good wiki needs footnotes, which I implement with the well working footnotes module. However, it is inconsequential and hardly user friendly to offer WYSIWYG editing when footnotes have to be coded using tags.

The obvious solution is to add a button to TinyMCE with a popup to enter the footnote text that automatically places this text in the [fn] footnote tags. elgreg seems to have done this for Drupal 5 with his TinyMCE footnote module, but I could not get this to work with my Drupal 6.13 and the latest versions of footnotes and WYSIWYG.

What is the easiest way to add custom buttons to WYSIWYG's TinyMCE editor? All TinyMCE tutorials on this refer to a block of code starting with tinyMCE.init which I just can't find in WYSIWYG's TinyMCE plugin.

Any help or directions is appreciated!