The paint on the plastic is different then what's on the body as it needs to flex with the plastic. So it's softer and must be treated gentler then the harder paint on the steel body.
There are products with varying amounts of abrasive and you should start with the least. I'll try to list in order what I would use that I keep in my arsonal.
A "Cleaner Wax".
A "Glaze" meant to cover light scratches.
A "Polish". Use light pressure.
"Rubbing compound". Last resort, BE VERY carefull with this.
You'll be able to tell quickly how much "yellow cab" you'll be able to remove but with luck and patience most all of it will come off.
After you've got it off use a good wax to restore the shine.
I can tell you from experience on my bumper that OEM touch up paint that works fairly well on the body but not so well on a small scratch on my bumper
