Advice on getting Ultimate Brilliant Flower to work?

I have unlocked the Ultimate Brilliant Flower move but have yet to be able to pull it off successfully. It’s the Hayabusa Ryu R1+X katana move where you hold it in to fully charge it, then press X again during the spin to pull off an izuna drop. I’ve tried doing this after my opponent is out of ki and after a successful counterspark but I just haven’t been able to pull it off. Was just wondering if anyone had any advice? Thanks so much.