Adrian, A few years ago when I worked for a big Expensive Daewoo yard I used to see them put the paint and fabric protection on brand new and used cars, them smart shield packs they sell you (biggest rip off!!). The paint protection is just a Teflon passed coating they put on your paint, it goes on just like wax with an application pad and then they buff it with a rag. No spraying involved. The fabric protection is just some chemicals in a spray bottle that they spray on your seats etc. The entire process takes about 25-30min max per car. So if I was you I would not be worried at all! When you do remove your spoiler there is most likely to be some dirt around and under where the legs were! And I forgot to add, yes it does wash out after a while just like any teflon based wax coating. They recomend that you re-apply the stuff every couple of years or something. But I recon just get some Gold Class Wax and it is the same. Good luck