A V-Buzz is a great tool for achieving a free and easy sound. To do this, place your front teeth slightly over your bottom lip, and move an easy stream of air through. Then, voice a mix between a "V" and a "W". The sound is closed in the mouth and vibrates a lot on the lips/nose. It should feel open, like an oval, in your throat.
Try using this trick on a few phrases of your song, then return to the words and see if you can maintain some of the V-Buzz feeling in your face (buzzy) and throat (open and relaxed).