Easy "Enlightened Guitarist" achievement
After unlocking "Through The Fire And The Flames", start a career under the Medium difficulty setting. Then, play through the song. When you are done, the "Enlightened Guitarist" achievement should be unlocked. This is much easier and faster than getting a "Gold star" rank twenty songs under the Expert difficulty setting.
To get the "Enlightened Guitarist" achievement without actually getting 20 gold stars on the Expert difficulty, enable the "Unlock Everything" and the "Hyperspeed mode" codes and set it to level five. Go into Career mode and play "Through The Fire And Flames" under the Expert setting. When you fail you should get the achievement.