Easier frame perfect rest OoS
By buffering your short hop out of shield with the C stick it is easy to get frame perfect jumps out of shieldstun.
If you don't know how frames work please refer to http://alexspuffstuff.blogspot.com/p/how-frames-work.html
inputs: blue = R, yellow = up C, red = down B
in game: blue = shield, purple = shieldstun, dark gray = jumpsquat, light gray = airborne, red = rest
In the above totally arbitrary and made-up example Jigglypuff's shield is hit with an attack that has 6 frames of shieldstun. Without buffering with C, jumping out of shield precisely when it ends on frame 9 would be difficult.
But by lightly flicking the C stick, you can buffer a jump over a wide window. If you can consistently flick the C stick so that it is read as up for 5-6 frames, you need only approximate within 5-6 frames when shieldstun will end. As long as the flick begins before the end of shieldstun and ends before the end of jumpsquat you're golden.
Due to the nature of being frame perfect with manual inputs it isn't realistic to expect a frame 1 of airborne rest every time, but given that a) practice makes this much more consistent and b) many rests OoS require a few frames of maneuvering to connect anyway this is not a big deal.
The import of this methodology is to achieve consistent frame 1 jumps OoS without having to drill specific timings.