I see where you’re coming from. In my experience, if I’m in a block, I physically cannot get the word out. Each time I try to cold open on the difficult word, my anxiety gets worse and there’s really no way I can say it. The things I mentioned have helped me have a better fluency rather than sitting there with my mouth open trying to say something for an embarrassing amount of time. If humming helps break out of the block and continue on with your sentence, that’s a win in my book. But like I said, everyone’s different. What works for me might not work for others.