In theory, a simple combination of Shine out-of-shield and Waveshine, this technique requires a frame-perfect jump cancel shine followed by a typical waveshine. If mastered, however, you can potentially turn a -4 hit on your shield into a full waveshine punish.
This technique is a brutal test of your ability to move quickly between jumping and shining, but with more practical utility than the infamous Multishine.
It is not possible for humans to execute frame-perfect techniques with 100% consistency, and not just because of human error. You might get just one input poll very early on the correct frame; then, even if you get the input in before the next frame, it will be too late.
For that reason, even the same exact input timing can lead to different results. If you input shine in the middle of the last frame of jumpsquat, for example, you may or may not be polled by the end of that frame. If you are, you will get the frame-perfect shine; if you aren't, you will be polled sometime on the next frame and get a frame 2 shine.