Let's see. I have a chuck resting right now. I would rest 20-30 min only if I was eating early but as friends just called moments ago and
will come for dinner after all, I'll rest longer. It is not necessary imo.
I do not subscribe to the 3hr/lb flow but I do not low/slow chucks. You certainly can; I don't. I do not use temp for finishing either. I go for fork tender.
Plan 50% but I get ~60%. I select roasts that are not internally thickly fatted, just very well marbled.
To give you an idea of today's flow in case you're interested:
I used precisely the approach described in
this link in terms of the quatre-épices for the rub and the wine/balsamic/sherry reduction. The chuck was 3.2 lbs and thick, about 3" or a bit more (I highly recommend thicker roasts). I used 7 med-small onions, about 1.75 lbs, and 5 cloves of garlic. (Both prepped as in the link.)
I salted the chuck, allowed it to moisten well then applied the q-e. I Minioned the start but used almost twice the amount of lit as usual. I added a little oak and a little cherry. The meat went on at 10:45am (it was 58 internal). The temp eased up nicely and I cooked at 305-311 till 1:10pm when I pulled it to foil. (Its internal was 158. I am not a temp stickler with chucks; it's more of a time thing with me. If the roast was thinner it would the internal would have been higher. I was figuring the cook at around 5 hours so I did not want to go much more than half that unfoiled. It was, as you see, 2:25 unfoiled.)
I don't have foil pans so at the 2-hour mark I made a 'pan' bottom out of two 18" pieces of wide HD stacked together. I put them on a small sheet pan then prepped the onions and garlic. I put half the onions on the foil in the center, tossed them with a little salt and white pepper and the half the garlic, drizzled with half the reduction, and topped with a thyme sprig. I then retrieved the chuck from the smoker, put it atop the onions, piled the rest of the onions on top of it, added the garlic, a little salt, another thyme sprig and the rest of the reduction, then put another 18" foil sheet over all and crimped all together, drawing the crimped edges up so as to create a bowl for the copious juices that will emerge from the chuck and onions.
Returned the chuck package to the cooker and raised the temp (over a bit of time) to ~340. I am not one to check the cooker much nor am I anal about temps so there were fluctuations (I'm sure; some I noticed) but generally the temp was 300-340 over the course of the next segment. At 2:50pm I moved the package to the grill table, carefully uncrimped two sides, then carefully flipped the meat over, nestling it into all the onions. (The liquid was plenty.) So 1:40 for the first foiling segment.
I went another 1:25 (till 4:15pm) and pulled it. I put it on a new sheet of HD, drained about .5 c of the juices over it, wrapped tightly, and it is now resting in the nuker. The onions and rest of the juices will be served with tourné potatoes and whatever else I can think of (gotta look in the fridge and see what I have).
Of course, different spicing, vegs, herbs, etc., can be used (and I do use other rubs, reductions and vegs but always use onion and garlic), but this gives you an idea of how I do them. This is pot roast style. Minor changes for pulled.