Magus420
Smash Master
You don't need to do anything to be able to do an up-b after a jab. Just jab then press up-b (you can buffer into it by a lot right after doing the jab, though you should really wait and react to seeing it connect first which is around when the jab's lag ends anyway).
To grab after a jab you can cancel the jab window to be able to grab without having to wait by shielding, walking, running, or crouching. I usually use shield+A if they're close enough, walk->grab if they're a slightly out of range, or dash->grab if they're even further away.
To grab after a jab you can cancel the jab window to be able to grab without having to wait by shielding, walking, running, or crouching. I usually use shield+A if they're close enough, walk->grab if they're a slightly out of range, or dash->grab if they're even further away.