I could only suggest a DiY
Minicobra explains it pretty easy.
Follow it and you should be able to repaint over the issue spots.
Rear Valance or Fangs blacked out
By the looks of it? it seems like its primer? what type of look are you going for? matte or gloss?
Ive done mine and I used bumper paint designed for plastic in matte from Pep Boys and have not had any issue