Paint & Body People! I have a question!
 

I purchased a used 3D Carbon GT500 spoiler from a guy off eBay who took it off his car after about 3 months. He ordered it unpainted, and had a local shop paint it for him. They did a horrible job and he took it off the car because the paint was bubbling and peeling.

So how to I strip the paint off of this thing to get it prepped to be repainted? I'm trying to keep costs down (thus purchasing a used spoiler) so anything I can do to prep the spoiler for a body shop to paint it for me would be good. If need be though, I'll spend the money to get it stripped right if it's beyond my capabilities.

What could have caused the paint to fail in the first place? The previous owner mentioned that it started failing after he washed the car. Could that have had anything to do with it? (Too soon? Bad paint? Bad prep?)

And lastly, the spoiler feels like a large hollow cavity. Would there be anything gained by maybe filling it with expandable foam to help it have a little more structure to the inside of it?

Thanks for any info you might be able to provide!