I have minor scratching and smearing on the front skirt of my car which is the plastic part below the bumper.
Is there a way to repair this without replacing the whole skirt?
The image below shows the location:
If it's a scratch just in the clear coat, then you can wet sand it with 2500 or 3000 grit paper and then use a buffer with a fine polish like in this video.
If it's more serious, like down to the plastic you'll need more aggressive sanding together with spot repainting. Here is a tutorial on how to do this.