I’m not sure if it’s called something different these days, but 20 years ago my speech therapists called it “easy onset”. Basically you would go through different sounds that weren’t vowel sounds and practice putting a cushion of air between your lips or very lightly touching your lips together to produce the sounds. So for instance, with the “m” sounds, you practice very lightly touching your lips together and then quickly releasing them. With practice and time it can help you ease into those sounds and can help prevent getting blocked on them. With the “n” sounds you just gently touch the roof of your mouth with your tongue and then quickly release. I personally would, and still do, use a combination approach. If I’m in a really intense blockage I would stop trying to push it out, release the air in my lungs, take a breath using my diaphragm and not my gut, and start over using the easy onset technique. Now this in general can be embarrassing because of the awkwardness of stopping mid sentence. It took me many years to accept how embarrassing it all was, but in the end I would rather be embarrassed trying to be fluent than stuttering my way through it. But this approach all depends on the individual. I frequently found when I did this I would be talked over in some way, usually the person trying to guess what I was going to say. But eventually I realized that everyone knows I stutter and hopefully they can respect that I’m trying. Hope this helps a little, I know there are many other techniques out there as well.