I really haven't, tbh. My dad showed me how he shot a blowgun though, which was to place your tongue over the hole of the mouth piece, blow, then move your tongue, so the air is forced out at once. I have always used this method. I can easily put a dart through a soda can from about 20 feet. Not saying this is an amazing feat, just that I can.
A good exercise is to inhale and hold for a count of five then for forcefully exhale and continue even when it seems you are done.You may even get a wheezing noise.The lungs are pliable and will stretch out even in just one session of doing this. Not to mentioned this is good for overall health and fitness especially if you smoke.
I do not personally use the tounge technique. However I have found that practicing the blowgun has increased my power and breathing. I read an article that linked blowgun use to overall good health. I will have to dig it up.
Chapter 2 in every one of my books is dedicated to realxation and breathing. After my heart surgery to years ago, I was intoduced to the "incentive spirometer". http://respiratory.healthcaresupplypros.com/dhd222500h $13 I'll post a picture of one in the gallery "Enhancements"
An incentive spirometer is a medical device used to help patients improve the functioning of their lungs. It is provided to patients who have had any surgery that might jeopardize respiratory function, particularly surgery to the lungs themselves, but also commonly to patients recovering from cardiac or other surgery involving extended time under anesthesia and prolonged in-bed recovery. The incentive spirometer is also issued to patients recovering from rib damage to help minimize the chance of fluid build-up in the lungs. It can be used as well by wind instrument players, who want to improve their air flow.
The patient breathes in from the device as slowly and as deeply as possible, then holds his/her breath for 2-6 seconds. This provides back pressure which pops open alveoli. It is the same maneuver as in yawning. An indicator provides a gauge of how well the patient's lung or lungs are functioning, by indicating sustained inhalation vacuum. The patient is generally asked to do many repetitions a day while measuring his or her progress by way of the gauge.
The breathing technique is the same used in "Psychoprophylaxis" (AKA in the US as the "Lamaze" method). This technique is what Dr. Hironori Higuchi used as his "Sport Blowgun Health Method" over a decade ago when he first published about using competitive blowgun shooting as a way to super-oxygenate the blood for recovering para and quadra-palegics and for seniors. If you watch a video about blowgun shooting in Japan - they almost always fo this technique prior to shooting. The raising of their arms above their heads helps expand the ribcage, allowing more complete airflow.
You wil even see David Caradine, Chuck Norris and Bruce Lee doing similar breathing exercises n their videos.
I play the Irish whistle/tinwhistle/pennywhistle, whistle for my dog and whistle at fine ladies (not really, not even the uglies).
I can't provide statistics, but I believe that these activities help my blow gunning. At least it helps at blowing out birthday candles, and there'll be 75 of them this coming April. Plus one for good luck.
I don't make any breathe control practices, but my friend does, and he says that it helps him. I think that it's not only physical, but also mental things are very important for every of us, and such resources and websites like this ( link: https://www.sunsigns.org/angel-number-707-meaning/ ) can open your eyes to different worlds and meanings, for example meanings of numbers and astrology signs, which can help you a lot.