This is very true for me, exaggerating facial expressions a bit was a big part of my last speech therapy. Practice opening your mouth a little more when you speak, I used to be embarrassed about it cause I thought I looked like an idiot but people don't notice it that much and it's better than blocking for 20 seconds on a word. When a scary word comes up, just open your mouth wider and engage your face muscles when saying the vowel in that word. If the word has no vowels, like some words in my language don't and all of those words have really heavy intonation or like hard R's or they can be said with your mouth almost shut, just connect that word to the previous or second one, act like it's all one big word. It does wonders. Don't be afraid to open your mouth, mimic a smile, exaggerate your A's, E's, O's, I's, U's and Y's. When you're at home, stick your tongue out up and down, left and right before making a phone call or preparing to speak, it's a muscle too, and a very important one for speech. Massage your chin and region around your mouth, even your eyebrows and eye region. Neck muscles too, for me my neck and eyes twitch when I stutter. I do this whenever I watch a movie, just massaging my face and activating my tongue and mimic muscles, looks really funny in front of a mirror or if someone walks in but hey, it helps. So basically what you said is true for me!!