I agree with Smoking Aussie, especially if the reheating equipment / capacity is unknown.
In the final stages of cooking pork butts, I boat (pan) them rather than foil them. To the pan I add 1 cup of apple cider / juice and 1 teaspoon of rub and then cover the pan.
When the bone just begins to wiggle I remove the pans from the cooker and then place them in the cambro / cooler and allow them to rest about 4 hours.
After the rest, I separate the drippings and refrigerate them for a few minutes. The fat will solidify on the top and some of it can be scraped off. I leave about 30% of the fat to maintain flavor, but not enough to have a grease bath. I pull the pork in the pan removing any undesirable large pieces of fat, cartilage, or membrane tissue. I then toss the meat in the juices of the pan to evenly coat all parts of the meat as well as to evenly distribute the bark. When the pork as started to cool down I then add up to 1/2 more cup of apple juice to the pan, cover it tightly, and refrigerate for several hours.
When chilled the juices will become gelatinous and will bond the pulled pork into a soft flexible block. Turn the pan upside down on your prep table or large cutting board and the meat separates from the pan.
Simply slide the rectangular block of meat into a gallon sized vac-seal bag, and properly vacuum seal the bag. These become flattened rectangular packages of meat weighting 4.5 - 5 pounds each which stack well in the freezer. I keep the weights consistent and even add extra to bring the weight up to the desired level. This helps to keep calculations on target when reheating for a large group. Because they are vacuum packed they will also keep very well for awhile in the freezer.
About 30 hours before the meat is to be served, I move it from the freezer to the refrigerator to slowly thaw. Thirty minutes before serving time, I bring a stock pot filled with water to a rolling boil. I put 2 packages per pot and move the burner to a low setting. After a few minutes I turn and rotate the bags of pork. Usually at the 15 minute mark the pork is thoroughly heated. Cut the bags open in put the pork in half sized foil pans and place in chafing rack with sterno under the water pan. Repeat this process if more bags are to be used.
The pork is very moist when served and tastes like it just came out of the smoker.
Vac-sealing the pork with the de-fatted drippings and/or apple juice then freezing it is by far the best method I have used.
Remember the pork is already fully cooked, so keep in mind that water boils at aprox 212° depending upon your elevation above sea level. Just gently heat the sealed bags of pork in the water, don't cook it. Boiling it in the package will further cook the pork, as will a crockpot. I get my best results by thawing the packages in the refrigerator 2 days before serving. I take a pot of water, bring it to a boil, then turn off the burner. Once the burner is off, drop the vac-sealed package into the pot of hot water and let it sit for 15 minutes before serving.
The pork is already fully cooked, you only need to bring it to a safe serving temperature of 145°, not to further cook it to a higher temperature.
I do this with many large cooks for My American Legion, VFW, and school fund raisers. I also keep 4 or 5 packages in the freezer for last minute gatherings and unexpected guests. For quick last minute thaws immerse the vac-packages in a sink of cool water for 30 minutes to fully thaw, then drop into the pot of hot water. This prevents the outer portion from cooking while the inside is still thawing.
I also find that using large 15 X 18 vac-seal bags and making the pork as flat as possible before sealing will allow even thawing and reheating.
