The stylesheet editor is useful for adding portal-specific changes / overrides to whatever CSS is being applied by DEFAULT.CSS and skin CSS files.  Although DNN supports dynamic loading of a default file name for a skin's CSS, there is nothing to stop a skin from including non-default CSS files as part of its code.  Thus it's entirely possible to end up with scenarios such as the "42" CSS files you (jokingly?) mentioned.
 
I often still get by with using only notepad for many basic edits but long ago I moved to using tools to help me drill down into the CSS so I'd know WHAT to go edit and WHERE it was.  I blogged about one such tool (free!) here:
 
  http://www.eguanasolutions.com/DNN_Blog/EntryID/19.aspx
 
With it I can highlight a rendered page element and instantly see all applied CSS as well as what file(s) the CSS is defined in.  The tool does much, much more than that but such tools are worth the CSS-features aspect alone.
 
 
Good luck!
-mamlin