Loading models/libraries in filters?

[eluser]behdesign[/eluser]
I'm trying to create an auth filter for my site, and I'm having trouble in loading libraries or models necessary to get the process started (mainly the session library to check for the ci_session cookie). I've tried loading the libraries directly with $this->load, but since it's not a controller, it doesn't work. I've also tried loading with $CI &= get_instance(); - also to no effect. I also have session and database in the autoload config file ... again, no joy.

How can I load libraries/helpers into a before() filter? Or what approach should I take to get an Auth filter to work?

Thanks.