Has Gajeel Use Dragonforce?

Natsu Dragneel, Gajeel Redfox and Wendy Marvell, all three of the First Generation Dragon Slayers, have entered Dragon Force, initially requiring an external catalyst to do so.

Does gajeel ever use Dragon Force?

Gajeel's attained other elements of power when he had to, and we've seen him use Dragon Force as well when he had to.

Can laxus use Dragonforce?

Whatever Laxus and Cobra used is definitely not Dragon Force. There is no reference to that, and the fact that they get dragon scales is probably because of that dragon lacrima. ... That's why we should write someting like "It is unknown if Second Generation can enter Dragon Force".