Best way to repair a ding on Spoiler?

I would try to level it a bit with the abrasive pen on a Dupli-Color applicator, then wipe it down with isopropyl alcohol, and apply body filler with indents. When cured sand with fine grit, try to keep it as localized as possible. Then a few strokes with the paint brush of the applicator. Dupli-Color Scratch Fix All in 1 - Universal Black CASF0100. It won't be perfect, but it's on an edge, and low, so not bad.

I've done bad things to ours more times than I can count, with the garage door...

 

I’ve found that the best way to protect the (vulnerable) edge of the spoiler is with a bit of prevention. In doing so, I’ve install rubber moldings on my garage door. Unfortunately, this was an afterthought, so I have several pre-prevention chips in the trailing edge. I’ve looked and looked for edge protectors of some sort but haven’t been able to find anything that would not look out of place. I’ve just resigned myself to living with it. Maybe some day I’ll sand it out and repaint the spoiler...some day.
BTW, don’t let the kids or the Wife, open the hatch without your supervision because, mysteriously, these chip just appear like magic!!!

 

I've managed to be the culprit for all the dings on ours...

Yeah I put some pipe insulation (dense foam tubing) on the trailing arm of our garage door opener. It helps somewhat. Usually it jumps the tracks a bit, which helps too.