Like everyone states prep is the key to dyeing plastic. I am in the middle of an interior refurbish.
I used bumper repair kit to repair broken pieces and to fill the holes in my original door panels where the map pockets once lived.
http://www.amazon.com/Bondo-280-Bumper-Repair-Syri...
On the parts that had dead plastic, I cleaned them real good. Then used a red scotch bright pad to clean off the remaining dead plastic. Cleaned them again, shot some SEM plastic adhesion promoter, then sprayed them with some Rustolumen truck bed liner to give them a uniformed texture. I let the bed coating dry for a week and then went back with a scotch bright pad and took the sharpness off the coating and got the texture to my liking. Sprayed them the color I wanted, let them sit for 24 hours and sprayed them with a plastic clear. I am going Torch red so I used dye from a corvette supplier.
http://www.semproducts.com/automotiv...esion-promoter
http://www.summitracing.com/parts/rl...FUoV7AodEWwATw
http://www.mamotorworks.com/Corvette...lding-601950-1
http://www.mamotorworks.com/Corvette...-12oz-106135-1
Pics of the results so far: