So, the matte medium was rubbish. No use. Failure. Luckily, I have learnt my lesson from past experiences and left myself a plan b. I bought some stickery paper that you print on, and have printed off my chosen final image on and stuck it onto the mirror. To be perfectly honest, I’m more than happy with the result. Yes, it doesn’t have the messy artsy quality that I love about modpodge transfer, but it does let the viewer focus more on the image itself, and lets the mirror reflect through stronger than it did with the mod podge. It looks more luminous. So with the glass firmly in place, I’m done. Voila.