The delay you are experiencing is probably from using a bit too much flash powder. You may want to get the touch-hole sleeved with an insert. Placement of the touch-hole relative to the pan is very important and can be pretty tricky. When things are right your flash powder flame will flick into the touch-hole and ignite the charge very fast. A few months ago one of our members here that goes by the name of 'salt' posted an excellent link that explains most if not all of what you are concerned about. Here it is
http://www.ninety-eight.net/ibha/flint1.htm#top