Darunia's BBBY is his most spammable attack. BBBBY is good for a focused attack on tougher foes. BBBBBY is powerful, although obviously slow to set up.
Agitha is definitely a pain to play as sometimes, just remember that you can avoid jumping onto the golden butterfly by tapping B rather than Y after combo attacks which summon it. If you do end up on the butterfly, then be sure to press Y rather than B, the B attacks are too slow, weak and clunky. BBY is surprisingly spammable since you can immediately dodge out as soon as the big circle appears on the ground.