Look up a video called the Nair chronicles.
Abate performs this technique regularly to good effect.
On the Hack pack you can put invincible shield on and practice easily. It doesn't take a lot of pressure to start to drop through the platform so I literally flick the control stick lightly and then press Z the instant the drop starts and then Z almost instantly again for the l cancel. Press Z yet again and grab if they are in shield. It's not technically demanding with a little practice! I actually think it's easier to do than most things in the game.
Like. Don't flick the stick back to neutral, just flick it down lightly and it returns to neutral on it's own