I only passed my OW because of 12-hour Afrin. (All of the different "sinus" or "cold" or whatever formulas are the same ingredient, just different labels--don't know how they get away with it but whatever...) Now, I'm not a doctor and I'm not going to tell you it's safe, and there was a thread on SB about Afrin possibly contributing to a O2 toxicity fatality, but that's what I did and I swear by the stuff. Before, I would equalize too hard and end up with blood in my mask.
The strange thing is, my ears have gotten used to it somehow, and I never need the Afrin anymore, even when out of the water for over a month. Maybe there was disgusting stuff stuck in my eustacean tubes that I managed to dislodge? ;-)
I would take the Afrin and start clearing even before I left my room. If one side wouldn't clear, I would help it along by plugging the ear on the opposite side. Then, under water, both sides would clear more easily.
I would also try some of the non-chemical solutions others have posted. And certainly use the 12-hr so it doesn't wear off during a dive.