Colour coding the bumpers isn't hard, i did it with my K10 years ago. Removing the bumpers on a k11 isn't hard, just fiddly because there are plastic covers in the arches to take off. It's one of those jobs where it's best if you clean the car 1st and get all the mud & crud off the plastics.
When i did my bumpers, i did no sanding at all, just cleaning. I wanted them to look the same way that genuine colour coded bumpers looked on the k10 so i masked off the areas that were suppost to stay black, gave everything a final wipe down to make sure there was no dust or anything, and then sprayed them with white primer (two medium-thick coats).
After that i put the red on (again two medium-thick coats) and then let it dry for 3 hours before laying on the laquor (which i slapped on in two thick coats).
I did not sand between coats, the primer clung onto the rough textured surface and the red clung onto the primer for the same reason, the laquor clung on but smoothened out and didn't retain the rough texture of the plastic instead it gave a nice smooth glossy surface.
After a week i simply t-cut the painted areas and then polished them, and what a shine (Y)
I would reccomend that you keep the stripe accross your bumpers black to give it that genuine look but at the end of the day it's entirely your choice.
Here's some piccys anyway...
Hope this has been helpful to you and good luck with the car. (Y)
