Hi, I've been stalking smashboards for a while but this is my first post so idk if I did anything wrong. Anyways, I found a quicker and easier way to true combo into that footstool combo you're talking about. Getting a footstool out of the blue is hard but the way I found, you can get it out of a punish, or approach with it since relatively safe.
Shorthop--> immediately throw metal blade down--> Footstool, follow their direction(it's always forward if you throw the metal blade to the front of their hurtbox)--> at the apex of your jump fast fall fair so that you hit with the later+weaker part of it cuz it jablocks then do whatever you want when they're forced to get up.
Late hit of fair jablocks til bout 50% and what I described above can be done from a fullhop too but you would have to fast fall after you throw the metal blade down to footstool them close to the ground.