Has it ever been revealed how They Work?
In John Carpenter's They Live, the technical aspects of the Hoffman sunglasses are never explained to the viewer. The closest thing we get to an explanation is they cause a strain in the optic nerve of the viewer if they are worn too long.
In later interviews, Carpenter explains the sunglasses are a metaphor to examine the idea that all advertising is a form of subliminal suggestion designed to slowly convince us to part with our money.
The more political elements of the film are derived from Carpenter's growing distaste with the ever-increasing commercialization of 1980s popular culture and politics, particularly the influence of Reaganomics, the economic policies promoted by U.S. President Ronald Reagan.
He remarked, "I began watching TV again. I quickly realized that everything we see is designed to sell us something... It's all about wanting us to buy something. The only thing they want to do is take our money." To this end, Carpenter thought of sunglasses as being the tool to seeing the truth, which "is seen in black and white. It's as if the aliens have colorized us.
Clark, Noelene (May 11, 2013). John Carpenter: ‘They Live’ was about ‘giving the finger to Reagan’. Los Angeles Times. Retrieved August 17, 2015.
The screenplay was adapted from a short story called "Eight O'Clock in the Morning" by Ray Nelson, in which a hypnotist reveals the nature of the world to the protagonist who has until 8:00 AM to reveal this invisible alien infiltration to the world.
Using the sunglasses instead of a hypnotist, allowed for greater narrative speed and story-telling padding to be utilized as well as creating a more focused US vs THEM storyline.
The metaphors of the sunglasses and their underlying mechanics are not necessary because it doesn't add anything to the story and can be skipped over without incident. The mechanic is simple and displayed in a scene clearly marking their capability.