Place onions in crock pot. Blend brown sugar, paprika, salt & pepper. Rub over roast and place in crock pot. Drizzle liquid smoke over pork.
Combine in a bowl vinegar, worcestershire, red pepper flakes, sugar, dry mustard, garlic and cayenne. Stir.
Drizzle about 1/3 of vinegar mixture over roast. Cover remaining mixture and put aside. Cook on low 8-10 hours. Take out meat and pour liquid out. Shred/chop up pork till fine and put back in crock pot. Add a little bit of reserved mixture that was put aside to only keep it a tad moist not wet.
Serve on a hamburger bun with your favorite coleslaw and a side of potato salad and hush puppies. Enjoy!