https://youtu.be/5dEaQ6GnZ3Q
Basically what you do is you jump and then press your second jump with your control stick pressed horizontally in the direction you’d like to go and then immediately after the second jump use magnet. It’s really not that difficult of a tech to perform and it’s harder to explain. You know you’ve got it down when you’re Magnet is gliding horizontally and you’re not stalling out. Just practice in training mode. Also make sure once you get it down you’re always aerialing out of it (Nair is the easiest to hit at first probs).
Also go to smashcords.com and join Ness’s discord. People will definitely be able to explain it well to you there
Yes, pretty much this....
One thing I'd add is that it helps if you configure the R shoulder button to jump. Well, it helped me anyway. This frees your thumb up to race straight to the B button so you execute the magnet as soon as possible after that second directional jump. The quicker you do it, the further, faster and more horizontal you travel. And the more likely you are to catch out your opponent.
It's also useful to do after an enemy knock-back at low to mid percentages. Much of time, you can fly right back at them for an easy hit, particularly if they are following up their knock-back move by running towards you, in which case they fall straight into your loving arms. By loving arms, I mean a rather punishing drag-down up-air followed by a throw or raise the roof combo.
Ness is quite a floaty character, which is a blessing in one way as he's more difficult to combo at low percentages, but, at higher percentages, it makes you very vulnerable in a disadvantage state as any grounded opponent will be able to predict your landing. Good use of the PSI magnet can scupper that and you'll find you live an awful lot longer. Just make sure you save your double jump.