Rating: 5 / 5
First you need a good shower of sparks. To get this you scrape the FireSteel with an acute edge. The back of a knife if square, the side of a Leatherman Wave file, back of a hacksaw blade, jig saw blade, etc. A knife edge works fine, but will dull the edge. My favorite is a spare 2.5 inch tungsten carbide scraper blade designed to fit in a Bahco or Sandvik scraper. They are available at www.amazon.com for around $7. Remember this is not natural flint, you do not bang it and the acute edge does not even have to be metal. You need a steady scrape along the rod either by moving the scraper or pulling the rod.
Second, although naturally found tinders will work start with the easiest. Get a bag of 100% Cotton Balls. Make sure they are cotton!!! They will light immediately with a spark. They become more water resistant and burn longer if swiped in petrolatum or petroleum jelly (Vaseline) There are many elaborate methods used to do this. I just grab the cotton ball, swipe in the petrolatum, and stuff in a film can. Grab, swipe, stuff, and repeat. To use pull one out and fluff. This is a favorite activity at the Girl Scout campouts I have been to, with my ferrocerium rods :-) , and how we have started our campfires.
A few comments. The ferrocerium rod will work after being wet, just shake it off and scrape. It can oxidize rapidly however, like a high carbon steel knife blade. So care needs to be taken. There is a larger model too which will last longer and provide a larger shower of sparks for natural tinders. The largest shower of sparks is probably available with a BlastMatch which only requires one hand and has a built in tungsten carbide scraper. One needs to squeeze and keep the rod straight or it can break, leaving one with a really nice 1/2 inch in diameter ferrocerium rod which will now require two hands. More information on such things is available at www.equipped.org. They have some small comparison videos and information on commercial tinders.
Have fun experimenting. In addition to "natural" tinders, other found tinders will work fine, cotton dryer lint, dryer sheets, wax paper, etc. Remember that tinder generally needs to have edges and air space.