I have done both ways. Usually I just do the cooler and foil method, but a few times I’ve used the 3D set at 140, but still wrapped the food with foil. I went this route the times I had a longer wait time before eating. Did a Wagyu brisket once, and it got to temp much quicker than I expected. Like almost half the time, so in the smoker it sat for some time wrapped at 140.