User blog comment:FairyRaven/Fairy Tail Chapter 470: Hybrid Theory, Review and Commentary/@comment-26042226-20160127060259/@comment-7418318-20160127190214

Wendy did go into Dragon Force at the end of the Avatar Arc without outside power-sources (except for eating air perhaps).... or at least Lucy called out "Dragon Force!" despite Wendy not showing the bushels of feathers we saw in the Tartaros arc, so maybe Lucy was wrong... or maybe it was a weaker form of Dragon Force or somesuch.

Regarding Gajeel, maybe eating Wahl (partially or whole) could do the trick. That'd be a sight to behold if he took a bite out of him or even ate him hole. ^^