Lead free paint would be fine I imagine. Just ensure you don't put it on too thick as to block air vents. I would ask the paint store if they can tell you the ingredients in the paint. Anything metal could maybe be an issue but I doubt it. I was playing around with this once for fun to see what it takes to kill a signal. Even wrapping my phone in foil paper did absolutely nothing. Could still ping it and it could still receive a call. You need pretty thick metal material to block a signal.