Hi McCaber....
I generally have the best results by (1) applying the base color/s (enamel on enamel, etc) and thoroughly dry, (2) apply good coat of Testors Gloss Coat.. place under a box to prevent dust... and allow 3 days to dry. (3) Apply decals and allow 2 days drying time, then (4) apply two more coats of Gloss Coat; 1 day drying time between them. (Results) A glassy smooth finish where the markings look to be part OF the finish instead of decals.
There are many techniques, this is the one I like to use.
Take care,
Frank