You'll find plenty information on this via the search engine as I did. I use a SFB with lump. I have no issues leaving it alone overnight. I do have concerns with unattended tanks connected to a fire. I've listened to bad accounts of leaving these things unattended. I'm just saying,,,,
Here's a former post I use when smoking a butt ( I don't remember who did this but thank you to that posting);
Preparation: About 12 hours before the meat goes in the smoker, trim a little if desired (I usually don’t), apply a coating of your rub of choice, and wrap in plastic wrap and put it in the fridge. (Some folks put on a coat of yellow mustard before the rub to hold the rub on and add to the bark. The mustard taste cooks out. This is a matter of personal preference.)
Smoking: Start your smoker and get it up to 225-240 degrees F. My personal wood choice for pork is hickory. Unwrap the meat, stick in the probe of your digital thermo (A highly recommended accessory.), and place the meat in
the smoker, fat side down. I don't flip butts as it interferes with bark formation. Fat side down helps protect the meat if you have a temp spike. After the meat gets over 100F I spray it every hour with a 3 to 1 mix of apple juice and Captain Morgan’s Original spiced rum. The sugars in the juice and booze will caramelize, and add to the bark. (Bark - dark outer crust that develop as the meat cooks.) Others will make good suggestions for alternate sprays. You will develop your own favorite with a little experimentation. (The nice thing is that they all taste good!) Foiling: When the meat gets to about 165F, double wrap it in Heavy Duty aluminum foil. Put some of your spray of choice in the foil to help braise the meat. At this point I usually stop making smoke unless there are other things in the smoker that need the smoke. (You can finish cooking from this point on in the oven set at 250F if the weather changes or you want to save smoker fuel.) Continue to cook until the internal meat temps gets to 195-205F. Remove the foiled meat from the cooker and wrap it (still foiled) in a couple old bath towels and put it in an insulated cooler to rest for at least an hour before you pull it.
The Plateau: Almost all butts (and briskets – but that’s in the beef forum) will hit a plateau where the temps of the meat stops rising. Don’t be tempted to raise the heat as that will dry out the meat. The meat is absorbing a lot of heat at this point while the connective tissue is breaking down. This is what makes the meat tender. Low and slow is the way to go! I’ve seen some actually drop in temp by a couple degrees. Patience – it may be over an hour before the temp starts climbing.