Blocking is extremely frustrating to me. I can go days without blocking a lot, then randomly, I hit a phase when I block so much I just give up on talking for a while. I have tried the passive airflow technique (a slow,quiet exhale followed by a slight prolongation of the first syllable in the first word ) which only works when I am relaxed. If I am in a stressful situations it has absolutely no effect because I forget to do it. More about passive airflow technique here: http://www.youtube.com/watch?v=EJimTW9x9UA