Hi and welcome to DV.

I havn't tried using an mp3 when trying to go lucid so I can't offer much help there. You should use the tutorials section as that offers loads of help when trying to induce LD's.
http://www.dreamviews.com/forum/index.php?showforum=16

Your method sounds like the wake back to bed method (WBTB). I would use the second method but stay awake for about 30 minutes to an hour.

Do you use a dream journal to help dream recall or do reality checks?

Hope this helps.