There are all kinds of "black trim" :think:
I've done it with KAIO on the textured black rubber GM used on running board faces and the tops of rear bumpers (Suburban/Yukon etc.). I've also used Pinnacle PCL on the black plastic trim on '80s VWs. But a) you gotta do it right, and b) it can mess up some types of trim if it abrades the texture.