Plastic adhesion promoter for painting fender flares?

I think they make them. But they are like 500 bucks. I'd smooth out the scratched ones you have with sandpaper and then grey scotchbrite pads. Maybe use a primer to fill in scratches?
Thanks, may very well try that. There is an automotive paint and supplies store called Space Age Paints near me that has an amazing array of products available for repairing and painting anything automotive. And may have something to fill in the gouges. They also have a mind boggling supply of various automobile fasteners for just about anything mechanically attached to a vehicle. Like a candy store for car guys.