The bumper strips are already black. They are designed to be flexible. They should have never been painted in the first place. The bumper covers themselves are an ABS type plastic and will take paint well. Have the paint removed from the pads and treat them with Armour All or whatever (your preference).

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.