I've been practicing this somewhat recently. I faced a Ness main who used this technique and applied a few aerials in the process. I feared having to do a full change on my control set up, but if you're like me and you have your set up set to default on the GameCube controller or made your set up the same as the GameCube controller on the 3DS, then you're in luck for some easy application.
On my 3DS, I have the following set up:
Tap Jump - Off (Doesn't make a difference here)
R - Shield
L - Grab
B - Neutral/Aerials
A - Jump (I use this to jump)
X - Jump
Y - Special
I jump with the A button on the 3DS, but in order for me to use my special (PKF) while jumping, I'd have to contort my fingers by pressing both A and Y at the same time, which isn't very practical. Instead, I press X + Y, causing me to perform a full hop and throw out PKF as soon as possible, then follow up the double jump with my A button (jump) while also pressing B (neutral/aerials). So far I've had success with this set up.
On the GameCube controller:
Tap Jump Off (Again, doesn't make a difference here)
R - Shield
L - Shield (I don't use this)
Z - Grab
B - Special
A - Neutral/Aerials
X - Jump (I use this to jump)
Y - Special
Basically the same thing, except the only differences are the buttons I use here and that I have two specials and one jump, whereas on my 3DS, I have two jumps and one special. Press X + Y to execute the Jump PKF (or PKF Jump), whichever this falls under. Anyway, hopefully this will help those who are reluctant to make big changes on their controller layouts.