If I want to seal the inside of my box as air tight as I can, but I want it to look nice on the inside, should I do a layer of fiber glass on the inside or is that overkill and there is something easier to do?

Want it nice on the inside (nice = solid white, and not brown board) so that if I install the lexan front and light it up, it wont look like *****! Any suggestions?

Also ill use MDF for the box unless I shouldnt for what im trying to do.