Hurrah, after a medium amout of elbow grease the spoiler end cap is now finished and ready to go onto the car. In summary the best method for a flawless finish is to rub back the paint with 2000 grit wet and dry paper. Use a paint renovator, bring to shine with a good quality polish and then finish with wax.
Only problem I have is should I put the finished unit back onto the car or use it as a mirror? The only additional problem is that the finish is so good on this one, I may have to remove the other and repeat the process!
When I have a chance (daylight) will snap a shot and share with the world!