Hey Robert,
Well it is pretty easy once you do it
Anyway I'll have to update the documentation for compojoomcomment on this.
take again a look at the docman plugin.
create a new folder called com_yourextension - it should have files like josc_yourextension.php and josc_yourextension.class.php
in your component you should do require_once(path to josc_yourextension.php) . What you need to pass as arguments to this files is an array or object with id.
look at the constructor in josc_yourextension.class.php - there you need to get the right id.
once you create this com_yourextension folder you should be able to create a new config in the backend for this extension. Once you have the config in place you should be able to see at least the read comments button in your extension.
To show the comments you should have a look at the check_visual function.
And another important function is linktocontent.
Daniel