I recently needed to reheat several pounds of pulled pork for guests. I was not happy with my previous attempts at reheating pulled pork - I tried the microwave and stovetop in a pan - and those methods didn't work well IMO.
I don't have vacuum sealed bags but decided to try zip-lip bags in a pot of simmering water and it worked reasonably well. The zip-lip bags are not as sturdy as vacuum sealed bags but with a little care the results are good.