Hi, I just did pulled pork for 20 people a few weeks ago. Just do what I did x 5! hehe. I love pulled pork and sometimes think I should have lived in N. Carolina instead of Texas (or at least spend some time there).
Here is what I did:
2 days before eating:
clean pork butts.
Apply mustard all over pork butt prior to applying the rub. The mustard holds the rub on and then conveniently "cooks out" leaving no mustardy taste whatsoever.
As far as rub goes.....everybody has opinions on this......

. Mine is simple (and Uppermost top secret) Shhhhh........ ok ok it's just sugar, salt, paprika, onion powder, garlic and cayenne.
Refrigerate for 24hrs.
1 day before eating
Remove from fridge & let sit for 1 hr prior to putting in smoker.
Bring smoker to 210deg F. I always use a smoker and have never done a pork butt with any other method.
Smoke butts until they reach an internal temp of 190deg F. This takes me 15-16hrs usually (low temp). Luckily, I have an electric smoker so I sleep pretty good while it cooks all night long. I only disturb the meat to take internal temp and reposition in the smoker to ensure all butts come out at around the same time.
Whenever I check the internal temp of the meat or reposition, I spray down the butts with apple juice, which keeps the meat moist. I actually put the apple juice in DS7's WDW water spray bottle cuz it's there (Y'all don't tell on me

).
Take pork butt out when done and immediately FTC ( wrap in Foil, then Towel, the Cooler) for a minimum of 1.5hrs (spray it down again w/apple juice just before wrapping). FTC really works, as the meat continues to cook as the temp comes down. It also ensures that you keep as much of the juice as possible in the meat.
After this, it is a simple matter to pull out the bone & shred using small salad tongs......... add the sauce and begin boasting!
Sauce
I use a simple vinegar sauce. It sounds like a strange combination of ingredients but people cannot get enough of it down here in Texas. I seldom have leftovers.....now ribs and brisket......yeah got plenty of that left.....
I found this recipe on the internet,and I am happy to share. I have been using it for years.
Vaunted Vinegar Sauce Ingredients:
- 1 cup Cider Vinegar (I use Nakano Rice Vinegar, Original Flavor)
- 1 Tbsp. Brown Sugar
- 1 tsp. Kosher Salt
- 1/2 tsp. Black pepper, fresh cracked
- 1/2 tsp. Red Pepper Flakes
Directions:
- Place all ingredients in a small sauce pan.
- Bring to a boil, and then simmer for 5-10 minutes.
- Let cool, and season pork to taste.
Above is enough for 1ea 6lb butt (cooked).
My thanks to "Habanero Smoker" a real American Hero
Anyhoo...........
Making pulled pork for 100 people is going to be a good bit of work.
I fully expect to lose easily 30% of the weight of the pork butt while cooking (it has a lot of fat and excess juice that departs during cooking).
I agree that 1/2 lb of pulled pork per person is reasonable if this is going to be the only entree served, "butt" (sorry bout that) if there are other entrees served I think you can cut it back to 1/3lb per person (JMO and you know your eaters better than me......

). Still, that is like 43lbs of pork butt (pre-cook)/ or 6 butts total to prepare and cook we are talking about.....YIKES!!
I generally like the pork butt to weigh between 6 & 8 lbs (pre-cook). Yes, you can do bigger, but I really like the "bark" er skin from a well smoked "butt" and want as much as possible in my mix.
Hope my comment help,hope your cook-out goes well & I hope you get some help....that's a lotta cookin'.
Sorry so wordy.....I got a thing for pulled pork......
So many questions, so little time.......