Based on the pic you posted.
Scuff it over with 400 grit paper.
Fill the holes with normal body filler and let dry.
Sand over with 400 grit paper.
Refill with body filler and let dry.
Sand over with 400 grit paper.
Spray with primer and let dry.
Sand out any inclusions with 1000 grit paper.
Spray with primer and let dry.
Sand out any inclusions.
Wipe all over with clean cloth and blow any dust off.
Spray base coat paint and let dry.
Check for inclusions if any LIGHTLY sand with 2000 grit paper.
Wipe all over with clean cloth and blow off any dust.
Spray another coat of base coat paint and let dry.
Spray with lacquer and let dry.
Spray another coat of lacquer and let dry.
If not happy with finish then spray another coat of lacquer and let dry.
If happy with finish then leave to dry for at least 24 hours if not longer.
Sand any inclusions lightly by hand with 2000 grit WET paper
Polish the scuff marks with what ever white body polish you have.
Better to polish the scuff marks by hand to save burning through the lacquer.
If there are still scuff marks after polishing in the paint then you have rubbed to hard with the 2000 grit paper and you need to polish again.
If happy with the finish then polish all over the spoiler to get an even shine.
Sorry if I went on a bit but I'm on holiday and have nothing to do atm
