Common household pressure sprayers with a hand pump, such as those you use in gardens, can cover an area with thin paint, stains or water sealers. You can apply thin water sealers to porches and decks with these types of pump sprayers. The key is to keep them properly pressurized with a hand-pump as often as necessary to atomize the material correctly. Stop and pump the sprayer whenever the material does not come out in a mist.
Take the top off the pressurized hand pump sprayer by twisting it in a counterclockwise direction and removing it from the sprayer container. This top will have a hand pump on the top and a canister on the bottom that is pulled out of the container. Remove this assembly and set it to the side. Fill the container with the thin paint, stain or sealer.
Set the top of the sprayer back and screw it back into place. Make sure it is fully sealed and that the hose and hand wand attachment are properly attached to the sprayer container. Pump the handle up and down until the spray container is fully pressurized, up to 40 pumps depending on the container.
Point the wand at the area you are going to coat with material. Hold the tip about 18 inches away from the surface and depress the wand's trigger. Adjust the pattern of spray by screwing the tip of the wand in or out to achieve the desired spray pattern and atomization of the material. Move the wand back and forth over the area, with a slow and steady motion. Coat the area completely, taking care not to make the material run or drip.
Pump the container as often as necessary to maintain a high pressure when applying the material. The higher the pressure, the better the coverage and atomization will be. Go over any areas with runs or drips with the paint brush or roller to even out the coverage for a uniform finish.
Most household paints will need to be thinned considerably with an appropriate thinner to be used with a hand pump sprayer of this type. Follow the manufacturer's directions when thinning your material.