It is probably around 1/5 mm thick and only visible from 3 feet away but I can still feel it a little bit if I go through it with my fingernail. I really want to fix it because it is like a foot long. Can I fix it with Scratch X or do I need to wet sand it? If I have to wet sand it, is there a way to buff out the dull wet sanded spot without a machine and which product should I use?

 

I would certainly give Scratch X 2.0 a try first.

 

Unless you have done wet sanding before you don't want to start with your MINI. It is difficult to do correctly and best left to a pro.
If you can't fix it with Scratch X you probably should seek a good detailer or painter (I have know many painters who wet sand not that repaint is the necessary solution).

 

I got it fixed with Scratch X today, and I also tried to remove some other existing contaminated areas with it but it didn't work... at least the scrach is gone.