Cut the pork shoulder into 2 inch cubes, this will not only cook faster, but you get to rub more spices into the pork and it will make it a lot easier to shred up later.
Make the spice rub. In a small bowl put brown sugar, salt, chilli powder, and oregano mix well. Keep 1 tablespoon for the BBQ sauce.
Working by tablespoons, add it generously to the pork and rub it in well, adding more spoonfuls and massaging until it is completely covered.
Put it in the slow cooker and add 1/4 cup of chicken broth or water. Cook on high for 4-5 hours, until it is very very tender.
Make the BBQ sauce, add all of the ingredients to a medium size sauce pot. Mix it, and simmer on medium heat for about 10 minutes. You should have a thick saucy consistency. Let cool.
Check in on the pork 4 hours in, and if you see that it is very tender then you can remove the liquid in the crock-pot. Start shredding the pork with 2 forks. Add 2-3 ladles of the BBQ sauce that you have made earlier. Remember to keep some BBQ sauce to add more on the sandwiches later. Reduce the heat to low and cook in the crock-pot for 30-50 minutes or more hour or until you are ready to serve. If you see that it starts to get dry you can add a bit more BBQ sauce.
To assemble the sandwiches: Lightly toast the kaiser rolls, put a slice of Swiss cheese, then add the pulled pork. Put 1-2 teaspoons of the home-made BBQ sauce. Top it off with pikliz, if you like it spicy and some pickled onions. I highly recommend you try out the pickled onions with the pulled pork it adds great texture and tangy-ness.