The blastmatch is good. The trick with firesteels and knives is:
- I can't see ruining a knife with a firesteel - that's a new one on me - unless somebody is scraping the edge down the firesteel. Now that would eventually wear a groove out of the edge, but who would do that?
- I've seen friends and even videos of firesteel "survival" tricks where the user is scraping the firesteel with the knife spine (correct) but using the power of their right arm (incorrect);
- the way I think is best to do it is NOT to use your knife weilding arm to scrape, but rather the muscles in your knife hand and thumb of the hand holding the firesteel. The thumb pushes against the side of the blade and the knife hand just bears down putting pressure on the spine and firesteel. It also tenses so as to prevent the knife from sliding off the firesteel and slamming into the tinder pile.
- doing it this way gives you a much better spray of sparks (molten metal), the molten chunks are bigger, and the knife doesn't mess up the tinder pile. In fact, the knife spine only slides about 3/4" or so along the firesteel.
Doing it as described above will reduce the life of your firesteel though, because more ferro is being scraped off with each stroke.