Rich, I have done a few real old plates, the old long ones.
Not really that hard, find the closest base color and paint the whole plate. then get a new sponge like you would use around the house. cut it in like one inch square pieces. Put the color for the numbers and or letters on a paperplate, dip the spong factory flat edge into the paint, dab it on some white plain paper so its not drippin off. Then carefully start dabbing the raised number areas and edgeing use light mutiple coats letting it tack up between coats. Take your time and they will look great. Good Luck
ebo