You can use the WordPress built in editor if you like, but that's a little tedious as well by the time you change permissions, and put them back when you are done. Have you considered editing "live" via ftp client or your hosts file manager? ( you MUST make back-ups just to be safe of course! )
Or if you like, a little safer and faster method - Firefox has some pretty good developer add-ons for "on the fly" edits from the browser. You can experiment all you like without actually making/committing any changes to your site until you find what actually works for you.
Firebug is by far one of my favorites.