Sometimes when I have like major blockages, I openly say "this word is hard for me to say, if you could be a lil patient," or I visualize the actual sound coming out of my lips and smooth the sound itself to flow out? Like I can't describe it. I try to use pyschological techniques with actual sound techniques. I tell myself that I CAN say this word, and to keep continuing. I also learned, to never restart the sentence because it makes it more difficult. Do you have a certain sound that's easy to pronounce? Sometimes I use a word thats easy to say before the difficult word comes and I speak sort of quick but smoothly and the easy sound offers a passageway for the difficult one.