What temp do I cook pull pork at?
Keep the dome at 250 degrees. This will put the grate at 220 degrees. This kind of cook can be done direct, but indirect is better. You really don't want 10+ hours of grease dripping on the coals.
Personally I would not recommend this type of cook without some way to be warned if your temp goes too high or too low. The most seen issues on BBQ forums all deal with temperature issues. You can eliminate this by getting a smoker and meat thermometer that will alert you when your Egg gets too low or two high.
There are several models that come to mind. On the low end there is the Polder and Maverick. On the high end there is the the BBQ Guru and Stoker. I'll let you decide which is right for you; however, I own BBQ Guru's DigiQ II, the Maverick and a Stoker. Even so my most valuable tool is still my Thermopen. It's instant read capability and accuracy are valuable for any type of cook.
How much do you need for X number of people?
What you want is 1/4 to 1/3 pound per person of finished product. You will lose 40% of the raw product after cooking. Using 40 people as a reference, you would figure 40 * 5.6 oz (1/3 lb.) / 16 (oz.) = 13.4 lbs. of finished product. Now devide that by .6 (60% cooked to raw) and you get 22.5 lbs. of raw product.
Older folks will eat less, younger people eat more. The number of side dishes will either increase or decrease this amount. It is always smart to figure an extra 20% into the end result.
How long will it take?
You need to plan this cook at 1-2 hours per pound. This is not total weight, but the weight of each piece of meat. Smaller pieces will fool you and finish later. So if you got a 6 or 7 pound butt you are looking at 9-14 hours total. This also assumes that you allow for space around each piece of meat. If you push them together then you are now looking at the total weight * 2(hours) for the cook time. Most butts will average around 1.5 hours per pound.
You want the meat to break the plateau. This is where the collagens and fat are breaking down to produce that Pulled Pork goodness. Normally the plateau happens around 165 degrees. It could be higher or lower and it could happen more than once. While in the plateau you may see the temp drop a few degrees. Don't panic, this is normal. It will rise again, but it will take quite some time. It is at this time that most of the total cook time is happening.
If you are looking to slice the pork you want an internal temp of 170-180 degrees. If you want to pull it you want the meat temp to reach 195 degrees.
A few last words of advice: Fill the firebox up to the top. Mix whatever DRY wood chunks you want for flavor into the lump. Make sure that NONE of the holes in the fire grate are plugged with small pieces. Light it and let the egg stabilize at 250 degrees. It will take 45-60 minutes to prove it’s stable. You want the smoke to be clear or very light blue.
IMPORTANT PART: Put the meat in with as much space between the pieces as possible. Close the cover. WALK AWAY. DO NOT mess with the vents. If you do you will be chasing the temp ALL night. Check it in about an hour. If the temp is below 250 degrees make a minor adjustment and wait a 15 minutes. Repeat if necessary.
Fat cap up or down?
Technically you can do them either way; however, lets put some logic to it. If you put fat side up you are putting the spices you rubbed into the meat toward the heat. It gets burned off and washed away with the fat dripping from the cooking process. Furthermore you have all that fat flowing through the meat. As the meat cools off this solidifies into grease. Fat really does not allow the spices of your rubs to penetrate.
Rub up the meat put the fat to the heat (down). As that fat breaks down all it does is go into the drip pan. The spices on the meat stay on the meat. And get pulled thorugh the meat as the collagen and fat breaks down. The fat give you that much more of a barrier between the heat and the meat.
What do I do if it’s done early?
If you are within 4 hours of serving then your best bet is to clean out a GOOD cooler. Line the bottom with towels. Tightly wrap each piece of finished meat in foil and place in the cooler. Cover the meat with more towels. About 30 minutes before serving remove the meat from the cooler and let it sit. About 10 minutes before serving, unwrap the meat and slice or pull it.
If your planned meal is more then 4 hours away slice or pull the pork. Place in ziplock bags and refrigerate. You really don’t want to take a chance on making your guests sick. About 45 minutes before serving mix the pork with some sauce or coke (soda) and place the sealed ziplock bags in boiling water.
What if it’s going to be done late?
Personally I’d order pizza for the guests, but that is me. If it’s broken the plateau wrap it in foil and kick up the dome temp to 300 degrees. This will speed up the cook. While it will be good it won’t be the best. Foil and cooking have a tendency to boil the meat in its own juice. It is better to just bite the bullet and let it finish cooking.