That stuff takes forever to cure man. Seriously... At least a week, but holds up nicely. Only problem, it does fade, quickly. The color eventually turns to a gray.
I would recommend, if you want the chrome gone, and changed to black, that you go with the duplicor Bed liner in a can. Scuff up the chrome with some light 120-240 grit sand paper, take some rubbing alcohol to it, and shoot it. Maybe even use adhesion promoter between the bed liner (in the can) and the rubbing alcohol process. Should come out nice.