Pat your pork shoulder dry with a paper towel. In a small bowl, mix together the oregano, paprika, cumin, salt, pepper, and olive oil until combined. Brush the mixture on the pork and place it in a slow cooker. Also to the slow cooker add the jalapenos, onion, garlic, and orange juice. Cook the pork on low for 6-8 hours or high for 4-5 hours. Once cooked, shred the pork and transfer all but two cups of it to a large airtight container. Place it in the fridge. Transfer the remaining pork to a large nonstick skillet over medium-high heat. Cook until the pork is slightly crisp. Keep it warm on the stove.