This is what I do when I don't have good tinder, and want to avoid wasting scrapes of the firesteel trying to ignite something.

YouTube - 002.AVI

Yes, I have found this method to be a viable option. However, I think I'm going to be more proactive and carry a magnesium rod:
http://firesteel.com/products/Magnesium-Tinder-Rod-with-Lanyard-Hole.html

Apparently, those magnesium rods from Firesteel.com are softer and easier to scrape than those big Magnesium bars from Coghlan's and others. By using separate magnesium rods, I can save my more expensive ferro rod to light 1,000+ fires.

I agree, I use the firesteel, scraper and mag rods from firesteel.com in my tinder/neck kits and they are superior to the walmart bars.