I just got a Si lip and is red, so now I wanted to paint it black
what kind of sand paper should I use?

I searched

 

use red scotch pad and just scuff it up. no sanding require

 

what is that red scotch pad?

 

I think he's talking about that stuff you use to clean your dishes. The green stuff is used on transmission stuff (at least at the shop I worked at), so I'm sure it's cool for body work!

 

how much would it run to paint just an si lip then?
if i do the sanding work

 

You should use some wet and dry sandapaper 400 grit and lots of water. If the lip has any little chips at all you should use 320 grit and lots of water. I would also advise cleaning it before and after with 3M wax and gease remover. The cleaner the better.