Haven't tested this with a mask yet, but here to tell you it worked insofar as I washed my glasses before pushing them up into my freshly shampooed/still damp hair tonight, which usually fogs them right up. They stayed clear as....glass...this time. V. impressed.

Edit: oh darn, this was the wrong tutorial to leave this reply on. What I thought I was responding to was the how-to I saw today, which among other things mentioned simply washing your glasses with soap and water, then letting them air dry or gently patting them dry yourself if you're in a rush (I did the latter). Which is working like a charm, so far.