H0SS302

hey guys. pretty crappy day today in south Texas.. so i was thinking about hitting up the hardware store on my way home from school to get everything i need to paint the panels i yanked out yesterday. (or get started rather, i figure a 2 day process)

my questions are-
What sand paper grit do i need to get(should i do a small grit right off the bat, or start with a smaller #grit and work my way up)
is primer the better way to go? or is it not really needed
What paint works best with plastic, iv read some stuff about using krylon plastic paint, but just want some opinions on it. i plan to spray black, so i do know to use "satin" black.

thanks guys, hope it quits raining.. i dont wanna be cooped up in the garage rattle canning it all day.