Most PC pads have a rounded edge that allows you to get into these areas. You have to be careful though. The EDGE2000 system is really good at this. It takes time and a delicate hand to learn this though.
You can always come back with and do it by hand it uneasy with the use of a machine.
The only way to get under your spoiler is by hand.
Thanks guys, I was trying to figure out how I could do the underneath of the spoiler when I did a test spot on the trunk earlier. I took pics if anyones interested
I don't know how it is on your car, but to get under the spoiler on my car (if it was still on) would be to take it off. Ours is 4 easy to get to bolts and it comes right off. Then you can just go right over it with the PC.