I've never tried the boiling technique, but it should work fine.
My leftover pork butt is usually frozen in Ziploc or Foodsaver bags. I vent the bag and microwave for 2 minutes at 20% power, stir the meat around, and repeat until hot. I think the trick is to heat slowly. I'm always impressed with how well it holds up. I don't notice any loss of smoke flavor.
I've also used a little apple juice, just like when basting during cooking, if I need a little added moisture.