Well there is no short answer... Basically the secret to getting long flakes with pressure is the same as getting long flakes with percussion. You have to have good convexity on the face your working. Which means taking short flakes sometimes to get everything right. This fact eluded me for a long time until one day it clicked. AHAH!! It was a good moment...
When pressure flaking build up of inward pressure before you snap the flake off is key. Also good platform preperation is a must... Somebody once told me that it takes a ton of rock to get it figured out. Literally! 2000lbs! Im well beyond that now and am still learning but I feel like Im starting to get the hang of it
Knap on brother! Go to knapins, watch as many knappers as you can. Read and watch videos online. But most of all keep bustin rock. Thats my 2 cents... Hope it helps
~Will