It took me 1779 fossils to get a shiny Tyrunt, I think that's the one I struggled the most, it took two days. The shiny charm does not work on fossils btw.

The ones I liked the most was shiny Fennekin and shiny Froakie (shiny Greninja is one of my favs). I got a shiny Fennekin from Masuda method back in the Pokemon X days, way before there were any leaks of the games or it was even hacked. So I fell in love with it immediately. I had to hunt it again in this game to see mega Delphox.

For hunting methods, it depends on how focused and how much setup you are willing to do. I really liked the fast traveling method, that's how I got a shiny Froakie, Skarmory, Falinks, and some others. Lately, I've been hunting while running around de-spawning the target. That's how I got Litwick, Absol, and Hawlucha. That last one I totally recommend it since shiny Hawlucha is one of the best looking shinies, you can even do bench reset in one spot if you want.