You mentioned safety to your grates. Let me also mention the health/safety risk to you (and your family) in using wire brush bristles. Even if they might not damage your grates, wires can pull out, stick to the grate, transfer to your food, and do some major damage to your digestive track.
I'm not saying I never use wire brushes, but you have to look extra carefully afterwards to ensure there are no wires left behind. For me that means having plenty of light, esp important at nighttime.
I found a stuck wire on a grate the other night. Another reason why using a wooden scraper (that's worn in to the particular grate I'm using) is really growing on me.