hey mate,
wet and dry is a very fine sand paper which needs to be used when wet, I'd recommend reading up on this first before going ahead and spraying your spoiler otherwise you'll end up doing it again when it peels/cracks. the whole painting this will take a day for the usual DIY'er at home.
1. prep spoiler by cleaning and drying
2. wet and dry sand the plastic surface, 1000GRIT maybe (I'm no expert mind)
3. Put down a couple of plastic undercoats (20mins between coats)
3. 3-5coats of VW rattle can, take your time start and finish spraying off the actual spoiler. (20mins between coats, at least 1hour before lacquer, some would recommend a day)
4. a couple of coats of lacquer.
For the fixing of the spoiler, I put 3 5cmx5mm (longxwide) strips along the spoiler, the rest was filled in with silicone. hmm.. I have pictures of what I did some where.



HTH, Garfay.