3. Take a Warm Bath
One of the best solutions by far is to take a warm bath. A warm bath will help you to relax and this alone will instantly reduce the pain and discomfort you might be feeling.
At the same time, the warm water surrounding your face and neck can help to further break up and dissolve phlegm and thereby encourage it to move freely and leave your sinuses.
Another benefit is that a warm bath can help you to inhale steam, which further breaks it up.