Back in 1960 I bought a British book on solid models. It became my Bible and its still today. I have read it at least 200 times!!!!! best book I have bought in my life!!!!!
About decals it taught me a very unique way:
Get yourself some " Brown glue paper" the one used many years ago that was used to "seal" packages. This you had to "water" the glue for it to stick...remember?
Paint the decal by hand on top of the glue. Once completely dry, cut the "decal" very carefully, place in water......the "decal" will separate from the paper then just "Re-glue" to your model...........The good old times were FUN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :D :D :D :D
a newer idea---I print say numbers for the side of a fus,fix it with clear unsented hair spray,when this is dry,coat the paper with elmers washable white glue,let dry,use enamel paint and cover the numbers with more than 1 coat,then use clear enamel over that after the color is dry,cut out,soak in warm water,slide the decal onto the surface,