Well, once you get to the higher levels of play you'll actually see A LOT of power-shields, so it's not as rare as may think. By putting your shield up at "random" times, you can bait reactions and habits out of your opponent. Also like I said before, shield tilting is an amazing tool to utilize, but you can't do it if you're only trying to power-shield everything. A good mix of power-shielding certain close range stuff and lasers/light shielding/and shield tilting will make you feel like an impenetrable wall against a player who's not so accustomed to seeing that stuff. Also keep in mind that you can tilt your shield while flexing it to create even more crazy mixups.
Get accustomed to the different degrees of your shield. They all come out at the same speed but you can "flex" your shield depending on what the situation is by how hard or light you're holding a trigger. Like if you notice someone accidentally does a sloppy dash attack into your shield you don't really want to lights shield because the lighter your shield is, the further back an attack will send you, so just hard shield --> shield grab. On the opposite side of that, if you're on the edge of a platform and you know they're going to try to hit you, put up a light shield and if they hit you, you use that property to your advantage and their hit pushes you off the platform, creating a free escape.