Everybody's brain is wired differently. For me, this did nothing. Besides, how is it going to help you with composing a shot through a camera's viewfinder anyhow? Are you supposed to turn the camera upside down before tripping the shutter? I just tried that. For some strange reason it looks exactly the same 🙂
What one would normally do (and this applies to anything already printed, drawn or painted) is hold the piece up in front of a mirror to ck it's composition. But that really was also no help to me because what looks great one way may look terribly out of balance the other way. The only way I was able to make lino cuts and etchings look right to me was to do the initial sketch as a positive to get the composition right, then flip it over to trace onto the block or plate.
I've been painting, printing, drawing and photographing for a long, long time, and with everyone I have met during all this time it has become clear that you either see the correct composition as you are working, or you don't. I suspect that no amount of tricks can help you if you have no innate sense of composition.
In any event, nearly all of the rules of composition that painters know apply to photographs as well. Like, wherever you have a human face, any human viewing the photo is going to look at that first. If you are trying to make something recede into the background's horizon on a colour photograph, put a touch of blue there. The most important thing to understand is how to use negative space, and the Asians were masters of this. If you're making a portrait of just one person it makes zero difference where you put them in the space, the viewer's eye is going to go to their face first, but you can make them feel things emotionally by properly using negative space. It's very easy to make the viewer feel tension or calmness by placement of the person in the photograph if you know how to do that. You can use also colour to generate emotion, or you can use it to change a composition.
And if you really know what you're doing you can break every compositional rule ever made and still have a great shot.