Mural

Hello a question regarding the cockpit windows of my BF110G by Eduard in 1/48. I applied the Eduard masks both inside and outside of the windshield and cockpit windows and painted inside of the windshield and cockpit windows with Mission Models RLM66. I started removing the masks but the paints peels off unevenly in splinters when I remove the masking tape. I am thinking of applying some matt varnish on top of the paint work in the hope that it will make the paint less brittle and stick it better to the inside of the windshield and cockpit windows! Any advice/thoughts? When the time comes to paint the outside of the windshield and cockpit windows would it be better to use some primer before spraying the paint?