Prep the ribs by cleaning and removing the membranes and rinsing with cold water. Season with salt and a light dusting of rub (maybe ⅛ cup).
Bag and vacuum seal the ribs.
Place in the water bath at 148° F / 64° C and cook for 24 to 30 hours. Make sure to cover the bath to prevent excess evaporation in such a long cook.
Remove the ribs from the water bath and place on the counter for 10 to 15 minutes, then submerge in an ice bath for 30 minutes or until fully chilled. This gives the ribs time to absorb some of the juices and to not shock them in the ice bath right away.
Refrigerate until you are ready to finish them in the smoker, up to 5 days.
Smoke the Ribs
Prep and preheat the smoker to 250° F for indirect heat cooking according to the manufacturer's instructions with a water drip pan in place.
Remove the ribs from the bag, leaving them wet as they will absorb more smoke and the rub will stick. Dust on ¼ cup of dry rub per rack.
Place in the smoker and cook for 1 hour.
After 1 hour, baste on the BBQ sauce on both sides. Continue to cook for 30 more minutes, applying sauce again after 15 minutes.
Remove from the smoker and serve immediately or wrap in butcher paper and keep warm in a cooler to serve later with more BBQ sauce.
This recipe is for one rack, but you will want to scale it up to more. Figure 2 to 3 people per rack depending on what else you are serving.
If your vacuum seal bags aren't large enough for the whole rack, you can cut the racks in half. Double bag if you are concerned about a breach with the long cook.
It's not necessary to preheat the water bath since the cook is so long.
Feel free to experiment with different times and temps for the water bath.
If you want more of a sear and color, you can lightly grill or torch the ribs after smoking.