This is the most powerful mind-clearing technique in the entirety of Taoist practice as far as I know. I’ve used it myself during times of extreme muddle-headedness to great effect.
It requires being able to blow the air along the top and sides of a relaxed tongue (yours), thereby rolling an ‘r’ and a willingness to keep rolling one for between ten to twenty minutes.
As you do, you’ll notice the centre of your brain receives a powerful vibration-massage, which opens it up, while effectively numbing the forebrain. This causes all the thinking to cease and the pure consciousness of the midbrain to take over.
The effect lasts for about an hour after each session but generally once is enough to clear up any outstanding issue that’s been driving you nuts.
I wish you absolute clarity and stillness.