Scrub the faded house numbers with dish soap and water until you've removed as much dirt and grime as possible. Let the numbers dry and use 220-grit or higher sandpaper to get rid of the metal’s sheen so the spray paint can easily adhere to the surface of the numbers.
Lay out a sheet of newspaper on your outdoor or well-ventilated work surface and place some crinkled up balls of aluminum foil on top. Put your house numbers on top of the foil to elevate them and ensure that the sides of the house numbers are not neglected when you spray paint. This also prevents the numbers from sticking to the newspaper as the paint dries.
Hold the spray paint can 8 to 10 inches away from the house numbers and gradually sweep the spray paint over the house numbers. Spray in a continuous sweeping motion, not stopping until the number is completely covered in paint. As soon as you stop painting, the wet paint will begin to blend, making the pass lines vanish. However, as you start again, enough time may have passed that a line might be visible when the paint dries. Make several passes until you’re satisfied with the result. Allow the paint to dry according to the manufacturer’s instructions.
Inspect the newly painted house numbers and check the sides to see if there are any spot that you missed. If you missed a spot, spray a bit of paint onto a piece of aluminum foil. Dab a toothpick in the paint and brush the missed spot with the toothpick. Repeat until all spots are fully covered with paint.
Mount your freshly painted house numbers on a spot where they are easily visible from the street to show them off to every passerby and guest.