There are many ways of relieving sinus pressure and clearing a stuffy nose, but all seem to be obvious to have or just some reminders.
Here's a non-obvious and strange way to clear a stuffy nose and sinus pressure, and fast.
Push your tongue confidently against the roof of your mouth then, press a finger between your eyebrows. Repeat same process for 20 seconds. It cause the vomer bone to rock, which loosens your congestion and clears you up in seconds.