Oh nooo, I hope you're able to get the tissue paper off safely!
I've made customs with so-called "matte" sealer before and the sealer still turned sticky. (AND ALSO GLOSSY, so much for being matte!) It might have been the particular brand I was using, but in any case I don't use sealer any more, I just paint and hope that the customs don't take a tumble off a shelf or whatever.