Just map them to be crawled in your meta tags. Include the code in your header template, and then vbulletin will use that header template on every thread/post that is made. In turn causing the search engines to spider the subsections of your site.
That thread was from back in 2001 before the spiders handled dynamic sites like they do today (or at least I have seen quite an improvement from them in the last 3 years).
vB3 includes a native archive for bots that can be enabled in the control panel. It masks the query strings (similar to those instructions), and culls images and formatting out of the threads and uses limited table structures.