Best way to prep a spoiler?

[Torch Red 10th]

Received my Saleen spoiler today, the one with no side pieces. Looks pretty good in general.

I had an unfortunate incident with a hub cap on the highway going 75MPH back in December at 5:00AM. Didn't see it in the road, hit it, blew right rear tire, destroyed rear bumper behind the tire. The tire didn't do the damage, the hub cap "fragments" did.

So I'm replacing the rear bumper and since they're mixing the paint, they asked if I had anything else I wanted to get painted. I decided to try a Saleen spoiler. I looked it over and there are a few small rough spots around the edges and one small spot on top. I don't know how well the body shop will prep it, so I'd like to get it the way I'd like prior to taking it to them. It's like a rubber composite almost. Fairly flexible. What's the best grit to get the rough spots out? What grit is best for finished prep before paint?

Any Saleen wing or body kit familiar people out there?

 

[VENOMOUS 10TH]

The less coarse the better. If primed before paint, then you could use 180 grit to sand the rough spots but if you're not having it primed, then 320 grit. If the rough spots are too bad, you may need to use some putty to fill the bad spots.
I would personally fix the bad spots, block sand the spoiler, prime, block sand, flexible sealer, base, flexible clear. Be careful though, if it is a soft rubber, stay away from 180 grit. You don't want to scar up the spoiler or mess up the shape of it.
Good luck
Scott