I'm sure you know, SJ, that the humidity level in the cabin is less than the Gobi Desert in August. I tell all the crew to keep a little spray bottle of saline solution and use it regularly… meaning once every hour or so. You have to keep the sinuses irrigated.
Additionally, being back there is a lot like being in grade school (in more ways than one) in that you are exposed to every airborne disease that comes in. Another reason to keep the sinuses well irrigated. Additionally, if you do have crappy eustachian tubes, producing the sensation in your ears that you describe, I would recommend against Sqad's advice on "force blowing" your nose. That only pressurizes the bottom of the eustachian tube forcing the congestion back up towards the ears. Rather, (especially during descent) hold your nose and swallow… which will help pull the yucky stuff down to the back of the throat and out.
The Brits I talk to )in aviation) mostly tend to using Otrivine, while our American crews usually carry a spray bottle of Afrin. Results are usually the same but don't overuse it.
I realize, explained by your questions concerning insertion of ear tubes, you believe this to be an ear problem, but all evidence seems to indicate (after talking to my overworked ENT) problems of this nature begin with barotrauma. It's amazing how many crews it affects.