I havent exactly got the best technique, I haven't done much of holding the striker and moving the steel. I started the by holding the fire steel and moving the striker towards the tinder. I haven't spread my tinder out by hitting it by accident yet but I have been close, so holding the striker makes a lot of sense.
Having the curve in the striker (or a V type groove) seems like a good way of keeping everything aimed as well as getting more surface area creating the sparks. I'm not really a fan of using the serrated edge, I am more likely to use that to make tinder scrapings. I prefer either the straight or curved edge for sparking even if it does need a little more pressure.
My EDC is always a Multi tool as the striker and a small fire steel with magnesium on my keyring. (a bit smaller and easier to carry than the Magfires)
My Magfires and some other firesteels are stashed in various grab bags and kits that I use.

I have recently got a couple of these fire starters to play with but I havent had a serious play yet. They are called "The Aussie Survival Tool" The wooden handle is designed to be tinder as well as the magnesium. Its an oily type of wood. (somehow I seemed to have built a small collection of firestarters)
www.the-firestarter.com