Most tennis courts have a small section outside of the fenced area. The most common industry name for this area is "the tennis court border". Too small to be squeegeed, it must be painted with a large paint brush. While this is common sense, there are a couple of "tricks of the trade" that can make the job faster and easier.
A border on one tennis court is approximately 360 feet long by 6 to 12 inches wide. That's a lot of back-straining work using traditional brush painting methods. Surfacing technicians figured this out a long time ago and came up with some simple adaptations. Rather than bending over to paint this area they tape the brush to a paint roller pole, allowing them to stand upright while painting. Most technicians use a 6" brush, but I have seen some use a small nylon kitchen broom. The small broom is especially useful if you have a wide border (12" or more).
The other ingenious little trick is to pour a bead of paint onto the surface before painting. This eliminates the constant dipping into a paint bucket. On a day with moderate temperatures you can pour as much as 60 feet of paint on the border before spreading with the brush. However, I would recommend starting with 10 foot strips (beads) until you get comfortable with the process. You can pour this strip by dipping a large cup into a 5 gallon pail of the paint and walking along the border as you pour.
The pros have refined this technique too by slightly modifying a large (1 to 2 gallon) plastic flower watering can to pour the bead of paint. First, you will need to enlarge the top of the opening so that it is easier to pour the paint into the watering can. This can easily be accomplished with a utility knife or small, fine-tooth, saw. Next, use the same knife or saw to cut the spout back 2 or 3 inches. The spouts are usually too narrow at the end to allow the paint to easily flow from the can, but widen as they get closer to the body. Once the modifications are made, fill the can with paint and walk along the border pouring a strip, or bead, of paint as you go.
The actual technique for spreading coating is more like squeegeeing than brushing. Hold the pole and brush like a squeegee and drag the brush along the bead of paint, spreading it over the border. If you have any excess paint after covering the border area, spread it so that it flows over the outside edge of the border onto the ground (assuming your border is not built against a retaining wall or walkway). If your border abuts a walkway or wall you will have to be a little more careful. In the case of a walkway or deck, you might consider laying masking tape to create a sharp, neat edge.
If this is the first time you have used a squeegee to paint a tennis court, it is also a good idea to paint a 6 inch section of the court along the fence on the inside, before you start the last out-of-bounds coat. This will eliminate the need to squeegee right up against the fence. You will still have to apply some touchup coating near the fence in places after you have applied the last coat, but it will be minimized and look much neater by painting this area in advance.