I have a Graco airless sprayer. We stack them on a sheet of Visqueen on the ground and fire away. With latex, by the time you get to the last stack, the paint has dried enough to second coat them. For cleaning the sprayer we just put a water hose in a 5 gal bucket and let it run. Lock the trigger on the gun, lay it on the ground, and let it spray until clean water comes out. Clean the pump filter and DONE! If I am only painting 10-20 boxes I just stack and roll them, brush the dadoed handle recesses.