Now, did you take that at face value? When you saw it, did you go, "why on earth does that gentleman want me to go for a walk in the nearby mountains?" Chances are, you didn't.
Why? Because you know it's a saying. You know it's figurative, and, if someone sitting next to you were to say what I paraphrased just a moment ago, wouldn't you think "boy, what's this *****e talking about?" Chances are, you would.
Now, granted, I'm not a big time stage actor like Kevin Spacy or Liam Neeson - I'm not very familiar with the lingo - and hell, sometimes celebrities say things that we mere mortals can't even understand (Mike Tyson: I'm going to rip his heart out, and feed it to his children) - but, to me, and many, "donning a mask" seems to be a classic ficturative statement for an actor - particularly one playing a character in which he has to...submerse himself into.
Now granted, I could be wrong, but hopefully if that day ever comes - and this thread gets bumped - people will just think I was joking around with all of this.