This is quite an advanced move for someone struggling with the game. The top girder fireball is never easy in DK.
As a point of interest, in D2K, you actually have to do the "line up the barrel with the fireball" thing a lot because there's a permanent top fireball on the L2+ barrel screens, and because the barrel screens involve more mandatory fireball-dancing in general.
The wrinkle is that D2K fireball-jumps are 100% controllable because fireballs always keep walking until they either hit an edge or a ladder they want to use. In DK their directionality is random and they can turn around and smoke you at any instant.