For twenty-five years of diving I used the maxim "If you can clear 'em going down, they *will* clear coming up." I was wrong. Five years ago, diving in Cozumel, I'd been having a hell of a time with ear conjestion and clearing, but was managing to get the job done with a combination of valsalva, swallowing, jaw thrusts, head tilts... all the tricks. Ascents were tougher on the ears than normal, but clearing - until the third dive on the fourth day, when the left ear absolutely would *not* clear. I went back down, came back up, went down, up, down, up *very* slowly... eventually had to surface because of depleted air supply, rupturing the left ear drum. Kept me out of the water for six weeks and left me with a permanent hearing deficit and tinnitus in the left ear.
Bottom line - if you're having a hard time clearing, save it for another day.
Rick