With the cost of paint, stay away from the airless sprayer, go to a paint supply place and get a cheap "gravity feed hvlp gun" and you will have the perfect combination to spray the amount of area your talking about. Make sure to completely and thoroughly clean your gun immediately after using it, before the paint sets up or be prepared to throw it away once the paint sets up. Dial it in so that you have a large needle for the thick awlgrip and then open it up so you spray a lot of paint when you pull the trigger. It can come out so thick that you almost get no overspray. But then be carefull so it doesnt get too "lumpy" with "orange peel" Takes a little practice , but results are worth it and its the cheapest way to do it.
By the way the "gravity feed hvlp gun" is the gun with the cup above your gun , hence "gravity feed. The other siphon guns need a lot more air to get the paint to the nozzle, and you get a lot more overspray because of this.
Harbor freight, northern tool, all have them.