I have never had problems with the paint chipping on the lower air dam. I used adhesion promoter prior to painting and it work out well
. Speaking about painting the bumpers and the turn signal bezel were chromed originally
on my car ….I prepped the chrome parts using a Sikkens material for etching the chrome prior to painting. That worked better than I even expected. I did also use Sikkens paint on the chrome parts.
Regards Rick