Yeah, I used one I got in Woodies a few years back. Think it was by thomsons. you need to powerhose drive well to remove loose grit, (not too well or it will remove tar between the chips) and just roll it on. I recommend a masonry roller, one thats supported on both ends of the roller, with a long handle, and a long pile.
It did bring it up almost like new. I say almost, because it's a little bluey in colour, as opposed to the original black, but it looked a hell of a lot better than it did before i painted it.