bumper scratch

[sub0]

Hello,

Few weeks ago, I scratch the real bumper a little. Not very bad but will a few black dots scratch mark. I went to the local paint store get the paint match up. I apply 25% reducer with 75% paint (was told) but when I apply to the bumper
using a spray gun (paint brush) looks like it don't take the paint.

I repair a little rust spot on my Carmy on matal and looks pretty good and no problem. It must because of the plastic bumper or I missing something to add to the paint.

THanks !

Sub0