Heat the vegetable oil in a large skillet over medium-high heat. Season the bricket pieces with salt and pepper, then brown each piece on all sides, adding garlic the last 2 minutes. Transfer the meat and garlic to a 5 to 6 quart slow cooker. Pour the beer into the skillet and simmer 30 seconds, scraping up the browned bits from the pan, add the beer mixture to the slow cooker.
Nestle the celery pieces around the meat. In a small bowl, mix the brown sugar, tomato paste, vinegar, mustard, soy sauce, bay leaves and paprika, then pour over the meat in cooker. Cover and cook on low 8 hours or on high 6 hours. Transfer the meat to a cutting board and let rest 10 minutes, then thinly slice.
Arrange slices on toasted rolls, drizzle with cooking liquid, top with cole slaw (if desired).
Cooking liquid is so delicious, pass it around or place in small ramekins for dipping.