There are two main categories of 0-shine run:

'Normal': Use the file cancel glitch to load a null file at the start of the game. The route is then basically just the regular Any% route, except you don't speak to Eddie at the start of the game.

Hover Only/No File Cancel: DON'T use the file cancel glitch, but instead, upon entering the castle for the first time, immediately perform FLUDD Early, without speaking to Eddie. Then, enter the hallway out of bounds area, move left to enter the lobby wall out of bounds, perform a double jump and start hovering with FLUDD. This puts you on top of the lobby area, and you are free to move left and enter the loading zone for Final Bowser. From there it's the same as regular Any% Hover Only.

Obviously Hover Only/No File Cancel is much more difficult, due to you not having Rocket or Turbo FLUDD.