What I am trying to ask is, did anyone ever notice him using Enton (IIRC Amaterasu) the same way they would use the Goukakyuu no Jutsu or Housenka no Jutsu? I think this can't be possible because it would requires him to literally "meld" Enton on his mouth or on the inside which will burn him unlike how Katon works, which is there is some space between the mouth and the fireball which doesn't make sense because it should still burn due to being too close to the mouth.