Just a couple of things to be aware of.
Before you start any painting offer up the supports to the the spoiler body.
The one I received and was warned about by Tracy (pendle lass), did not fit well and needs sanding down to get a good fit.
If you don't do this preparation you will end up with a gap
The whole spoiler and supports will need rubbing down prior to painting as they are not a smooth finish.
After drilling holes in the boot
You need to paint the bare metal to prevent it rusting before fitting the spoiler.