1. Fasten your seat-belts, check the mirrors and preheat the oven to 350 degrees F.
2. "Are we there yet?" In a small bowl, combine the black pepper, oregano, cumin, celery salt, garlic powder and paprika.
3. Rub the spice mix well into the meat and place the roast fat-side-up in a foil-lined pan. Bake for 45 minutes to an hour in the pre-heated oven, or until the internal temperature in the thickest part of the meat reads 120-125 degrees F.
4. While the tri-tip cooks, make the BBQ sauce. In a medium saucepan, over medium heat, melt the butter and saute the onions and garlic until soft and golden.
5. Add the mustard, brown sugar and instant coffee to the saucepan and cook for one minute, stirring constantly.
6. Stir in the hot pepper sauce, tomato sauce and vinegar. When the mixture comes to a boil, reduce the heat and simmer 30 minutes. Check and adjust seasonings.
7. Remove the meat from the oven and let rest a few minutes before slicing thinly across the grain and returning to the roasting pan.
8. Slather the meat with plenty of warm sauce and return to the oven.
9. Heat the buns, pile high with barbecued beef and smother with gobs of warm sauce. Place the sandwiches precariously onto flimsy paper plates.
10. Hop into the family wagon (beginning, yet again, another rousing chorus of "99 Bottles of Beer on the Wall") and get back on the open road, secure in the knowledge that your upholstery will never, ever look the same again.