i love autocancelling falcon's dair and making him say "TUAHH" without having any move come out
if i had AR tech skill i would do that in front of people's shields, then grab
edit:
rotate the control stick with your left thumb, and with your right hand you may either rotate the c stick, or mash a/b/x/y/z (whichever you can do faster)
the key is to recognize when you ****ed up and are getting grabbed and begin mashing before you've even been grabbed
i'm pretty sure that this is a widely-held misconception
c-stick doesn't help you wiggle out when you're grabbed, it's only rotating the control stick that helps. also, L, R, and Z work (i think z, i know L and R do.)
the thing is, though, if you're at high percent you don't want to wiggle the control stick as much, because if you get thrown you might not get a chance to react, and you could botch your DI and die. the speed depends on the throw, but it's often times not worth the risk of getting out a little earlier.
Also, if you wanted i'm pretty sure you could repeatedly tap the direction you want to DI on the stick to help wiggle out, as well as the face and shoulder buttons, since any of the 4 main directions count as an input to help you wiggle out. I'm assuming that returning the stick to center and tapping any direction also counts as 1 input.
the same thing applies to spamming L/R; you can ruin your tech window if you hit it at the wrong time, so at mid/low percents you might not wanna.