Yikes this is difficult. I’ve trimmed and attached 1/2 of the backscene, and made plenty of mistakes. I’m using archival PVA glue and maybe started laying the printed sheet in a larger swathe than I should have, creating a few air bubbles that can’t be pressed out.
On the areas where I did try to go back and smooth things down, I inevitably scratched and gouged the delicate printed surface (it is only paper, after all). Then I went over the sheet with Testors Dullcote in an effort to protect it from further harm, but the nozzle on the spray can was gummed up and spat drops of dullcote rather than providing a nice, even coating.
Oh well, it looks pretty good for all that: