Does anyone have any experience using the product Forever Black? It's a permanent dye that restores color to bumper and trim. Then it says that it should only be used on porous surfaces. How do I know if my surface is porous? I had posted in another thread about having scratches on my B pillars, and in my searches online, came across Forever Black. I was wondering if it's worth using, but figured I'd ask around here first. Thanks.