Well my brother and I have done some catering on the side and what we usually do is after the meat has been cooked, we seal it in vaccum bags (Foodsaver Machine).
At the place we are going to serve, we bring large roasters (ones you can roast turkeys in). For pulled pork or burnt ends we put meat in them at low temp for about an hour. Make sure to keep an eye on it and stir the meat around so you get even reheating. If you need to, add some finishing sauce to keep the meat from drying out while your reheating.
For ribs or sliced brisket we place a metal rack in the bottom of the roaster so the ribs or brisket arent touching the bottom of the roaster. Then we poor a very small amount of water and have even experimented with other liquids (experiment is still in progress, but apple juice has been the best so far). After about an hour of reheating the meat is warm and moist.
Obviously the reheating time will vary based on the amount of meat your reheating. What we've found is do it slow to avoid drying out the meat and burning some of it. And if it wasnt obvious, take the meat out of the sealed bags before you start reheating it.