That’s what he’s doing already but you only get the current scene’s noodle run as a post process. Render layers cannot be included in node groups.
I like to create a separate (master) scene for rendering only. It only contains a camera (scenes won’t render without one) and only render layers from the other scenes are loaded into the compositor. This is the only scene in which I generally set up a node network other than for testing purposes. This keeps me from ever needing to append node groups which can sometimes be more trouble to connect properly than to just rebuild. It takes an extra second or two for each frame to render this way but it also keeps the compositor organized and somewhat sane.
At some point in the future when macros are introduced (v.2.50) node groups should (hopefully) become a useful “One Click” method for adding prebuilt effects (especially those which are dependent on certain types of complex matte setups) without having to do all that re-piping.