This cook requires very little monitoring.
Season the Tri-Tip with Montreal Steak Seasoning and garlic. Then vacuum seal and freeze.
Into the 127°F water oven, still frozen, a few days later.
I leave it in there for about 12 hours. Six hours is probably the minimum.
EDIT: Plunge it into ice-water for an hour or two to completely chill it then store it in the refrigerator until the day you want to serve it.
Remove it from the vacuum pack and put it into the smoker at ~400°F without patting it dry (try to make plenty of smoke) until the internal temperature reaches 132-135°F. That should take about 1¼ hours.
Wrap it in foil for about 15 minutes, slice thin and serve.