You're not a robot and could probably not make an even enough coat to make it useful. Also, any imperfections would be glaringnly obvious because you stare at the screen when using it all the time. Another thing to consider is that you may reduce the overall visibility of your screen due to imperfect coverage and the type of "matte spray" you are using. Acrylic matte spray is for paint and "projects" that require extra protection, not for screens.
It would be easier to just clean your screen enough to put the coating piece over than try this endeavour.