I dont know if this has been a topic already but...
If you user the up-man and time the snap you can sometimes scream through the middle and block the fg or extra point.
I've had a handful of blocks so far, and have had 2 or 3 blocked (thats how i learned the method)
Its risk reward though, as you have to have everyone rushing so its susceptible to fakes. (Got burned on a rollout once or twice)
Try it out.
(I dont consider it a glitch as it will sometimes get blocked up and again, you have to time it near perfect. Thoughts)