It'll look poor tbh mate. Viynl smoothed bullets with little white stickers for the letter would look nice, viynl rear wiper plate and even the rear wiper plastic itself (if you still have a rear wiper) would look nice too. Also the wingmirror plastics, i.e the base plate and the surrounding plastic where the painted cap stops.
Its the suble little touches that look the best imo.
The spoiler will just look like its not been painted yet from a distance.