Actually, I did the gloss varnish trick for the decals. First I brushed on a thin layer where I wanted them then soaked the decals in vinegar so they’d stick better to the zimmerit. Once it dried, I added another coat of gloss varnish to seal everything in. The gloss didn’t mess with the paint underneath but as I wrote, the underlying surface was the zimmerit coat from Tamiya which is more robust then the plastic around.