Another thing that I've started incorporating with my play is catching stage items like benches and then releasing them with shield to cover aerial approaches. They just sort of slowly float upward when you shield release them so they can get in the way of crumpet dashes and air dives.
Here's something new I discovered last week. While in standby mode when the Slam meter is full, if you powershield an object back and forth enough times and slam the other player because of it, you will be able to still slam, but the actual red glow around you will disappear when pressing B and you will not get any points at all when hitting other players. .
Nah, I slept through the comet that wiped out the unicorns!