Any tips on masking a 72 dart grill for paint?

I did my 71 grill myself. Took about 7 hours. First off, the black areas are natural black plastic, not painted from the factory. I spend a few hours with a tooth bush and Q-tips cleaning the black plastic with plastic cleaner and conditioner. Then some minor sanding of chips and edges. Another cleaning and then masking and paint.
Used 1/4", 1/2", 1" amd 2" tape and an Ecxato knife.
Grill restoration places want around 600.00 to do it but they painted the black which is not correct and I didn't want that.

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