I used homemade (inkjet) decals on my Curtiss Jennie kit (current thread in airplane forum). At the last minute I realized I had overlooked small registration numbers on rudder! I realized I could make these easily by merely resizing the big numbers decals for the fuselage. However, I had already done an overcoat of a couple of light colors to fade down the decals, and didn't want to do any more of that, and feared trying to limit spray to just the area of the new tiny decals would show. Now, on the fuselage numbers I had used black color, which then was faded with the overcoat. I decided I could make the new small rudder decals look faded by changing color to medium-dark gray. It worked great. A photo is in the model photography forum.