The attack you need him to do is a horizontal fire breath. And you do a jump attack, it's as simple as that.

The timing of the jump attack is relatively precise but not too bad.

The important thing is for him to do the horizontal fire breath.

As long as your timing is right, & the angle on the jump attack is right you should have no problems.

If he charges forward his position gets messed up and you'll have to quit out and try again.