I've played with fire steels for a lot of years, since I was a kid I always thought they were neat. Pre-dating finding the magnesium, Doan's type fire steels, one of the earliest instructions I received was to slowly, carefully scrape the fire steel into the tinder. Once you have a little of the fire steel scrapings on the tinder then strike the steel normally. The little pile of dust sparks up and helps light the tinder. Essentially its like directing your sparks exactly where you want them to go. I've had success doing this on natural tinders though they are always harder to light.
Be ready thouggh, sometimes you end up sparking them before you're ready.

Dave