You can get everything you need for simple black and white address curb numbers at your home improvement store for under $25 plus a few things you probably already have around the house. There are many complex and colorful designs you can do, but if you've never painted a curb, start with a basic black numbers on a white background or white numbers on a black background. Colorful designs aren't that hard either, but unless that's your entire focus, stick with something simple.
Here is a picture of an upward facing curb numbers I painted without any sort of [protective coating in May of 2008. Since this was right next door to where I was living at the time, I was able to watch it over a period of years. I watched it in fact for over 4 years just so I could monitor how long a curb number would last, painted this exact way. (See the "after" picture below)
I recommend Rustoleum brand flat enamels, which I used for all my curb numbers, including the ones in the photos on this page. You can check out complete curb painting toolkits at kit.com, where I compiled images and links to all the various products I use for everything. Be sure and check out my basic kit and my advanced kit.
To start, figure out exactly where you want the numbers to appear on your curb. Using the 1/2" masking tape, tape your numbers together lining the stencils up along the edges. If you use Cole Brand oil board stencils your numbers will be about 1" apart.
Cole numbering stencils used to be available at any home improvement store, but the "Numbers Only" pack is no longer available on their website (or in any store I've looked in, and I've searched), so I recommend looking around. Cole still offers numbering stencils, but you have to buy the whole alphabet along with the numbers and the cost is about triple what the numbers only pack used to cost.
This is the exact same curb number in April of 2012! I did nothing to encourage or discourage it's life...I wanted to know how long a curb painted "my way" would last. In fact, it lasted through the summer of 2012 and still looked pretty good, and I wish I'd taken more progressive pictures. But I think you can see how long the curb number can last.
Once you locate the spot for your numbers, use a heavy brush to knock off the dirt from the curb, then mask an area 5" high by 11" wide (for 3" Cole Brand stencils). This width can vary depending on the actual numbers you are painting. For example, if your address is 1111 Fox Avenue, you will not need all of 11 inches.
Tape your numbers together, then measure the combined width, then add 1-2" on each side. You can tape some newspaper around your painting area to protect the surrounding area from over spray. Then simply apply your background color. If you want white numbers, apply a black background. Use a back and forth motion and lightly cover the entire area, paying attention to the edges and corners. Continue spraying until you have good coverage. Rough concrete requires a little extra paint. Let your background dry for a few minutes until the surface feels dry to a light touch.
Once your background is dry enough to apply tape to it, center your assembled number stencil to the background, and tape it securely on all edges. Mask the remaining background from getting painted.
Paint the stencils carefully using short bursts of paint. You can wear rubber gloves and use your fingertips to press the edges of the numbers as you go and that will minimize under spray. Once complete, you can remove the stencils immediately and allow the numbers to dry a little.
If you have some under spray, spray a little paint into the cap of the paint can and use a small brush to touch up any areas that need it.
Finally, remove all your masking and you will have new curb numbers that should last for years!
The curb number images shown at the top of this page were painted on an upward facing curb in Dallas, Texas which endured several hail storms, 2 ice-overs and the other regular heavy Dallas storms over a period of basically 4 years. It was painted exactly as described in this article. Since then I have discovered that you can spray a clear protective coating on top and get more years life out of your curb numbers. That is subjective though, and you can skip the protective coating and still get great performance from just the paint, if you apply it properly.