Crimea_River
Marshal
Interesting approach that I've not seen before. Have you tried just using some ground graphite? Rub a pencil on some sandpaper, load up a paint brush with the graphite and gently apply to the model building up slowly. Easily wiped off glossy surfaces if you're not happy (on matte surfaces, not so much) and can be sealed with a clear coat when you're done.
It's usually not a good idea to put tape over decals as you and I both discovered.
It's usually not a good idea to put tape over decals as you and I both discovered.