I model Irish Railways CIE & GNRI From 1960's to 1990's.Some are kits & others are bought and kitbashed. some are made from scratch. All rolling stock is wheathered which i think makes all the difference & realistic.I love to see other peoples work & i know how many hours it takes, but it's worth it.
Can I ask, do the 3 x 20ft floors need to be removed to put containers on?
Can these wagons hold 45ft and 30ft containers?
And can the little lugs for holding containers be placed where needed?
You could try washing up liquid and hot water, it should come off if you rub it with you finger nail.
Anything more could mark the surface and avoid the numbers/lining. Do you have a picture of the loco?
Up close shows every thing, but it won't be seen.
I usually cut as close to the decal as possible so the carrier film is less visible
but the light catches the top edge.