On top of what GMaster said, getting your late Nair > Shines down is important. If you REALLY don't wanna get shield grabbed, do a shine grab after your shine. Once you have more respect from your opponent, if he's a heavier character, I usually like to waveshine behind their shield and start drillshining, and when they roll away continue to pressure them with either more late nair shines which at this point will probably shield poke, or a drill shine > waveshine up smash if I catch them quick enough to get a dair on them.
Repeated Nair shines isn't really necessary to learn. I don't really see the advantage to pressuring like Mango does with repeated Nair shines, it's very unsafe. I think maintaining overall stage pressure and doing safe on shield attacks like, for example, a Nair that just taps the shield, late Nair shines > early backaway Nair or shinegrab, is better. It doesn't give opportunities for your opponents to do ANYTHING since all your attacks are safe and you can really maintain control of the stage by simply doing safe attacks.