Easy BBQ Pulled Pork Sandwiches

1 pork shoulder roast (about 2 1/2 pounds)
1 bottle (about 14 ounces) BBQ sauce (I usually add a little more because we like it saucey)
1 T. Fresh lemon juice
1 T. Brown sugar
1 medium onion, chopped
8 buns

Place roast in the crock pot and cook for 10-12 hours on low or 5 to 6 hours on high. Remove the pork and shred. Discard any liquid in the crock pot. Return the shredded pork to the crock pot and add in the BBQ sauce, lemon juice, brown sugar and onion. Cover and cook on low for 2 more hours or on high for 1 more hour. Serve on the buns.