I too have found it difficult to use the magnesium bar and flint.  The only way I have been able to make it work is to use a leaf or somthing to hold the many flakes I need and then place my tinder on top of the flakes once I can get them started.  I now prefer the Light My Fire fire steel to the magnesium and flint.  It is more reliable.  I can make fire in much less time.
John