The fastest way to get the smoothest finish with latex paint is to use an airless paint sprayer, which you can rent for less than $100 a day. (Other sprayers are less expensive but require you to thin the paint to a precise consistency.) As you follow these spraying guidelines, be sure to wear a disposable respirator and cover anything in the vicinity that you don't want paint droplets to land on.
Prime the sprayer. Fit the gun with the proper-sized tip (see TOH Tip, below). Then stick the sprayer's siphon tube in a clean bucket of paint, and fill the sprayer, hose, and gun according to the instruction manual.
Set the pressure. Turn the sprayer's pressure-adjustment knob to the lowest setting recommended by the paint manufacturer. Hold the gun 12 to 14 inches away from a scrap piece of cardboard or paper and spray a test line with one uniform stroke of your arm. If the paint spits out of the gun or two thin lines appear above and below the main stream, the pressure is too low. Turn the knob up slightly and test-spray another line. If the coverage is too light or there is lots of overspray, the pressure is too high. The pressure is just right when the paint flows evenly out of the gun in a single stream.
Spray the edges. Hold the gun tip 12 to 14 inches away from and perpendicular to the edge. Apply the spray in one fluid motion so that an equal amount of spray goes past the top and bottom edges, as shown above.
Spray the faces. Hold the gun tip 12 to 14 inches away from and perpendicular to the face of the door or cabinet frame. Using the same smooth, uniform motion as above, overlap each pass by 50 percent. Flush out the sprayer. At the end of each day's spraying session, remove and brush-clean the gun's tip and spray guard. Stick the siphon tube in a bucket of clean water, and pump the water through the sprayer, hose, and gun into a waste bucket, according to the instructions in the manual. Continue flushing until only clear water comes out.
TOH Tip: You can find the specifications for a gun's tip size and sprayer pressure for the paint you want to use in the technical data sheets on the manufacturer's website.