If Wilson breaks the fourth wall in this movie, then it needs to be very, very subtle. Maybe like this:
Wilson and another character are standing 3 feet from each other, talking. Camera view is behind and over the right shoulder of character X, looking at Wilson from mid-chest up. Wilson breaks eye contact with character X, and looks directly into the camera three times during the conversation. Character X, out of frustration, looks over his right shoulder, directly into the camera, and asks Deadpool, "What the hell do you keep looking at?'
Wilson says, "You ever get the feeling your being watched? Or that your stuck in a reality TV show that you are unaware of, like that Jim Carey movie?"
Character X, "Your effing crazy, you know that? Crazy!", and he stomps off.
Or:, if you wanna go for sheer stupidity...
Wilson goes to a restroom, approaches a urinal, and starts to do his business, all the while seeming to hold a conversation with someone else. The camera just does a static shot from about five feet behind. Wilson double takes, looks back at the camera, and says, "Hey, let's keep this PG-13, pal, give me a minute. Besides, I don't want this to end up on the internet, like that _________ website."
The named website could be SSH, CBR, Newsarama,AICN, or whatever.
The problem with placing it after or during the credits, is most will simply assume it one of the gag or blooper reels, and not realize that is part of the character.