Can't help you there. No 3DS, nor do I plan on getting one unless it gets really big down here.
Regardless, there's no reason why the stuff I said shouldn't work in a game with less magnetic ledges.
Edit: friend has the demo
Edit 2: expanded theorycraft.
Falcon: shooting him mid up B makes him shoot straight up, leading to an easy cape. Shooting him mid Side B basically cancels the move. With cape's nerfed range, I wouldn't be surprised if he can grab Mario from a cape attempt with up B. We'll have to wait and see on this, but, regardless, FLUDD destroys Falcon Dive and Raptor Boost.
Bowser: Up B OOS has always been a great tactic for Bowser. Bait it, land with FLUDD instead and shoot him into the air for a free punish, or off of the stage for a free gimp. Like most moves, shooting him in the middle of it to push him up and set up a free cape.
Bowser jr.: his up B will get destroyed, probably his side B too.
Charizard: it destroys his up B too, and with no gliding, he's even more limited.
Lucario: eh, we'll see. I don't remember FLUDD being that effective vs. him, but there weren't many Lucarios around me either.
Doc/Mario: Up B OOS is very risky around a charged FLUDD. If you whiff, you die.
Duck Hunt Dog: I think his up B is a Duck carrying him? You can FLUDD him to force him to miss the ledge sweetspot. Free cape and/or punish. If he tries to fly over and past you, FLUDD him off the stage. If he resists that, you still get a free punish.
Fox/Falco: Their up Bs get pushed a lot mid startup. I'm not positive on how side B will be affected, and it may be less useful since Fox and Falco don't go helpless from it, but this will also depend on the lag after the move.
Ganon: same as Falcon
Greninja: not sure, but probably similar to what happens to Pikachu when you shoot him mid quick attack.
Ike: lol. Ike has to base his recovery around FLUDD. It stops quickdraw and it can push Aether very easily.
Link: if you ever catch link without a double jump, he should die to FLUDD. If you FLUDD link while he doesn't have his jump, he has 3 options.
1: do nothing, and get caped because mario can move before him after using FLUDD.
2: Up B mid FLUDD, go Straight up, then proceed to get caped.
2.5: Up B right before Mario capes him, and die because his up B needs momentum to go any horizontal distance.
3: Airdodge through the water and die from being unable to make it back. FLUDD's water will also eat any projectiles he throws trying to cover himself.
4: Up B OOS and in general is risky for him with FLUDD around. If you shoot him, he goes helpless and most likely offstage.
Little Mac: his recovery is already terrible, but to add insult to injury, you can shoot him mid up B and expect him to go flying because his up B only goes straight up.
DeDeDe: FLUDDing super dedede jump makes it go mostly vertical, setting you up for an easy cape. If he tries to go over you, shoot him off the other side. If he tries to mix you up and retreats back towards the ledge, FLUDD him off.
Lucina and Marth: FLUDD them to stop their aerial momentum and go in for a cape. If they up B early to hit you, they won't have enough momentum to make it back. If they wait, they get caped. If they miss an up B OOS, they die.
MK: He misses an up B OOS, he dies. With no glide, FLUDD will probably wreck his new up B too. I've heard tornado has increased ending lag? Shoot him at the end and force him to go helpless, or just shoot him off the stage.
Luigi: FLUDD's water halts green missile, and if he goes for an up B and misses, he either dies or takes a free punish.
Ness: Shoot him so his PK Thunder misses.
Zelda/Sheik: If you FLUDD the startup of their up Bs, they will never sweetspot the ledge. If you FLUDD their landing with their up Bs, they get pushed up into the air in helpless. Death or punish either way.
Villager: Jump at him with your back towards him. If he tries to go really low with balloon trip, Dair and pop his balloons. If he tries to fly over you, FLUDD him off of the other edge, or he takes a punish and is put back into the same situation. If he tries to go straight towards the ledge with balloon trip, shoot him and force him to miss. What's he going to do?
Olimar: same as villager, except even more limited.
Pikachu:
https://www.youtube.com/watch?v=eP2TOzPBRIA
https://www.youtube.com/watch?v=93m2PzwaEjg
Pit/Dark Pit: I already feel bad for these two. Shoot them mid up B and drastically alter their flight plans.
Rosalina: shoot her mid up B. Laugh.