Not trynna sand down to metal, just get down to the primer, then primer and paint

Also, how many cans, ive got 8 primer and 8 color currently

 

Youre spray bombing your car? Youll need about 30 cans. Youll need a good clear coat also and wet sand he orange peel after.

You dont have to sand to bare metal unless youre going to use filler. If youre going to repaint, just scuff up the surface and shoot your base than clear. Prep the surface very good before anything

 

If you're just wanting to sand the clear coat on the car, I suggest using 800 grit, then rattle can the hell out of it afterwards. It's going to look good for a week or so, then turn to ****, but it's your car and you can do what you want. Most people here would suggest using real car paint

 

Unless the current paint is cracking and peeling then you dont have to sand it down to primer. You just need to scuff up the paint with 600-800 grit.