When I want fast ignition with a flinter I use floured blasting powder, bought it for a dollar a pound when a rock quary when broke. Its about the same granual size as baking flour and it does not have any graphite added.
Back when my Grandfather was teaching me to shoot he had a little wood morter and pistle and ground his own from regular black powder. Lee
P.S. If you ever grind any black poeder use only wood or you might set it off .