I actually shine out of shield my flicking the analog stick up to tap jump out of shield, and then slamming it right back down and pressing B to get a grounded shine. It was really easy for me to pick up because it's similar to the way I perform double laser from the ledge. You're gonna get a lot of up B's out of shield when you're first learning it, but keep at it and you can make it work. I also felt like I was able to wavedash out of this shine a bit faster from this method than when I tried using Y, but maybe that's just me.
And as Bones mentioned, I urge you to not shine OOS with the c stick. In a perfect world, you'll get a frame perfect shine OOS every time. But the fact of the matter is it's impossible to consistently react to and gauge the exact shield stun of every single move that hits your shield to a frame perfect degree. The shield stun of a move can even change based on stale moves, and keeping track of all that in the middle of everything can be a mess.