Why can't I access IIS Manager on my server with Reporting Services installed?
As of SQL Server 2008, IIS is no longer used by SQL Server Reporting Services. It utilizes the HTTP.sys API now. So you will not see SSRS show up as a site or application pool.

The tip you linked to deals with SQL Server 2005, which required IIS in order to use SSRS. This tip speaks of the slowness you might be seeing and how to address it in SQL Server 2008/2008 R2. I would test to see if the same results are seen in 2012 version.