I saw a website with a great idea. The hard part is getting the raised letters painted in the accent color. For me in TX, the plate is black with white letters. Prep by removing and fixing any rust or damage. Prime with good primer, several coats. Paint entire plate white, 4-5 good coats. Allow to flash and dry. Spray 4-5 good coats of clear. Let dry overnight. Paint the black with 4-5 coats and again dry overnight.
Wet sand the raised parts of the letters gently with 400 grit or higher. The black will slowly sand off revealing the white underneath. Just don't burn through past the clear and white. The edges will be nice and sharp. Allow to dry and clear coat to seal.