I tend to use "uh" or "like" before certain words that I know cause me to block. I wouldn't recommend it at all however because like others have mentioned it just adds to the problem in the long run. People look at me weird all the time when I say "uh" five times within one sentence. I'm trying my hardest to not do it any more but whenever it takes me 5 minutes to get the word "tomatoes" out to the guy making my sandwich at subway or any place where I feel pressured to speak, I start getting desperate.