Best Method for Mass Deleting Splogs/Users

Just curious as to what everyone considers the best way to delete a whole bunch of splogs/users.

I have a wpmu 2.9.2 that was allowing open blogs/users to sign up and have a basic blog for free and upgrade for "supporter" benefits. It has sadly been neglected over the past 7-8 months and Is full of splog signups and users.

If I wanted to do a mass delete of all non-supporter blogs (the ones that aren't paying - cause truly, no non-paying blogs/users are legit on this site) how would I go about this?

Using the wp-admin interface only allows me to delete 20 at a time and I'm looking at thousands of blogs to be deleted. Is there a way to safely delete these blogs/users directly from the database?