Your tricks for dying different color door panels.

Anyone have any tips to keep dye from scratching off door panels after changing colors?

I got a really nice used set of white door panels and dyed them black with the spray on stuff from eastwood.
I just used one coat, maybe shoulda used two coats because the dye seems to scratch off easily with a fingernail or shoe when entering/exiting car.

Is there a clear coat protectant that can be sprayed over the top coats when all is done?

Just a side note: I scrubbed the door panels first with mild detergent and water, then used some good quick evaporating brake kleen and a white terry cloth towel to remove any grease or anything before spraying the dye.