I was working on a Jayhawk helicopter in the Coast Guard livery. I had to remove the windshield/side window piece 'cause I had forgotten to take one of the pieces of masking tape off of the INSIDE before gluing it in place. By the time I discovered this, the model was all painted. When I glued the piece back on I had prominent seam/crack at bottom of both door windows.
I had been working with a couple of homemade decals for the project and had some pieces of blank decal paper sitting on the bench. Had an idea- painted a couple of stripes of red- to match door red. After paint dried a cut two very fine strips from the paper, just wide enough to cover the cracks. Used them as decals. Worked great!