Hello, i am going to bouild my magic mirror (i am waiting for some parts, like the LCD driver), I’ve tested a very cheap two way mirror film on a little glass frame. Not sure i’ve clear as i should before applying the film, infact there are some imperfections. I also remember you all that the film has one (in certain cases, two) protective film for the reflective side. That side is “stickeable” on the back of the glass (the inner part facing the outside part). On internet you could find a lot of tutorial. I share here the result of this very first testing, pulling the glass “filmed” mirror on a led monitor.
I like the result (more than enough for the money).
Monitor without mirror

Monitor with a glass panel with a mirror film