I can't find the link for this method but I read it the other day and it seems to work... In essence, it says that airways and sinuses often close because of too little CO2, quick breathing and mouth breathing. So, close your mouth, take a breath in and exhale slowly through nose and then pinch it shut and hold your breath. Nod your head up an down while holding and keep holding until you feel the big urge to inhale. Inhale slowly and repeat 10 times. This allows CO2 to build up, which is good, causing airways to dilate.
I have tried it and my sinuses opened up dramatically, but mine seem to be swollen and not pure congestion from mucous.