If you can see the black ABS plastic you're through the lacquer, paint and primer and probably have grooves, gouges or deep scratches.
All depends on how visible and how good a result you want.
Halfords kits come with primer, paint and lacquer (clearcoat). No matter what you do it will always be rough and obvious looked at closely.
To do it properly you'd need to cut back to a smooth edge, fill any marks, smooth again, then spray primer, paint and clearcloat.
Big job or a professional to match in or panel spray.