I have used the method in the original post, and have had success.

I also plan to order a few of these:
http://firesteel.com/products/Magnesium-Tinder-Rod-with-Lanyard-Hole.html
Those magnesium rods are reportedly softer and easier to scrape than the tradition bars mentioned in the original post.

Carrying a magnesium rod will make me fee more secure, and it's just a tiny bit more weight. I feel like I can start a fire almost anywhere with a ferro rod, magnesium and a scraper. I also use petroleum jelly and cotton balls. Likewise, magnesium is also waterproof and can also be used to help light natural tinder found in the wild. Plus, a magnesium rod will last for 100+ fires according to my estimation. In the same amount of space, I estimate 10 fires max from PJ and cotton balls.