We posted a tip from reddit earlier, on how to get rid of a stuffed nose. Now here's another tip from user gymfork. It's a clever acupressure method that apparently solves the problem in 20 seconds.
Push your tongue against the top of your mouth and place a finger between your eyebrows and apply pressure. Hold it for about 20 seconds and your sinuses will begin to drain.
Instead of pushing against a specific point, just push it flat against the top. When you let go you should feel a little movement at the back of your throat, and that's the sign of a sinus saying goodbye.

Try it.