On the S4 it is not necessary to touch the radiator to remove the spoiler or the front bumper. It is a bit of work, and access to some of the fasteners is hard, but it is quite doable.To get that piece off the car is a LOT of work. You have to drop the "cooling package", the radiator and condenser coil and oil coolers. Probably a better way is to mask it well and paint it on the car.
However, it is also possible to paint it in place as mentioned