Kaivaan kind of mentioned this, and I've used it with some success. Making up lyrics... not to be incorporated in the music... just for the lead instrument to follow. If you have a solid progression composed, this'll be pretty easy. Like humming, with the structure and phrasing that language has naturally. Sure... sing in English, French, or whatever other language you know.
At first it might feel pretty awkward. But then I realized I can make up the silliest, most vapid, terrible lyrics ever and not mind, because they'll never be uttered to another human soul.

Will the melody be logical?... it sure will. It'll even inherit some flavor of whatever raw, basic attitude was present in the unspoken lyrics.