I made some dry ribs (just half a rack for wife and I to split) last weekend, and put the rub on completely dry (historically have used mustard) and then spritzed with apple cider vinegar every 45 minutes or so. It was a new hey grill hey recipe, supposedly Memphis style dry rub. No wrapping, cooked at higher temp (275) and spritzed.
If you are going with a mop/spritz, you do need to open of course. I would just try and minimize. Figure out your cadence (every 30, 45 or 60) and try and resist peeking in between to keep the heat up and smoke circulating.
Can't remember if you got a smoke tube, but I've become a huge fan of them. The pellet smokers are super simple, and I wouldn't want to mess with an offset smoker, but the pellets are low in moisture content and made more for consistent burn than smoke production, so I now use smoke tubes to add more smoke from a combination of pellets and chips.
Here's a highly rated one on Amazon:
Amazon.com : LIZZQ Premium Pellet Smoker Tube 12 inches - 5 Hours of Billowing Smoke - for Any Grill or Smoker, Hot or Cold Smoking - An Easy and Safe Way to Provide Smoking - Free eBook Grilling Ideas and Recipes : Patio, Lawn & Garden
What I do is a handful of pellets, then a small handful of chips, then handful or so of pellets, small handful of chips, etc, until full. I make sure the top 2" or so are just pellets. When lighting the tube, you want a couple inches of pellets to make sure it lights well and stays smoldering, and then the pellets will burn up the wood chips, which add even more smoke.