I hope it goes well for you with the decals. I tried that technique on my grille bar letters without success. Those little letters are really flimsy and really sticky. My fumble fingers could not make it work. I ended up painting the grille bar the white grille color with catalyzed acrylic enamel which has a fairly long window for clear coat, then spraying the letter area with the contrasting base coat color when the acrylic enamel was near the end of its time window. I used 1000 grit wet paper to sand off the unwanted base around the letters as it is very soft and easily removed with light pressure. Washed the whole thing then sprayed clear. Its been several years and no complaints yet. That is how I would do it again.
