I too suffer from constant post nasal drip. The only time it subsides is if I go to Mexico where the air is apparently cleaner. Went to an ENT specialist and was prescribed Atrovent Nasal Spray. Although it helps the post nasal drip, I can't use it very often because it ends up causing a sinus infection. If you are not prone to infections, you might want to ask your doctor for Atrovent.

Another note...it seems like the updside down treatment is for infections. Let us know how it works for you.