You're describing McRibs, not good BBQ. I have never, NEVER had a brisket or rib roast that was served with anything more than a dry rub and maybe some au jus. Same with pulled pork. It's should be served dry and then be the diners' option to add a sauce.
And sauces don't necessarily need to contain HFCS. Most recipes obtain their sweetness from boiled down cherries, molasses, or perhaps at most ~2 tablespoons of actual table sugar.
You honestly either have no idea what you're talking about, or have been exposed to a lot of [Mark May]ty cooks all your life.
Rub. Before it is cooked, many of the best Texas barbecue joints simply use "Dalmatian rub": Liberal amounts of
Morton's kosher salt and coarsely cracked black pepper. For them, stylin' is to add some cayenne and garlic powder to the rub. Some leave it on the meat overnight in the fridge, but others just season the meat and toss it on the pit. Leavving it on overnight is a good technique because the salt will start to penetrate. The other spices won't but you want that NaCl flavor amplifier down in there where it can also help the proteins retain moisture. On the competition circuit many cooks use a complex secret concoction of herbs and spices that give a little spark to the
bark, the flavorful crust that forms after all that cooking. I use my
Big Bad Beef Rub.
Slather. You can put a rub right on bare meat, or you can help it stick by moistening the meat with a little water, or you can put down a slather of mustard or ketchup, or you can use cooking oil.
My experience that they make little or no difference in the final outcome. Mustard is water, vinegar, and maybe white wine (all mostly water) with mustard powder mixed in. The amount of mustard powder is so small that by the time the water steams off and drips away, the mustard powder remaining is miniscule. If you want a mustard flavor, you will do much better by simply sprinkling it on the meat.
I usually use a cooking oil because it helps keep meat from sticking to the grates and because most of the herbs and spices in typical rubs are oil soluble, not water soluble.
Then again, salt is water soluble and, as we explain in our articles on marinades and brines, salt is pretty much the only thing that penetrates meat more than a fraction of an inch (with seafood being the notable exception). So using mustard might help dissolve the salt and using oil might help dissolve the hebrs and spices.
Far more important is what is in the rub than under the rub. So use whatever you want for a slather.
Pump. Many competition cooks like to inject brisket with an internal marinade by using large hypodermics and other gimcracks. These "pumps" add moisture, break down tough fibers, and add flavor. Many of the champs have been injecting the meat with a product called
Fab B Light or
Butcher BBQ Brisket Marinade, both moisturizers, tenderizers, and flavor enhancers. Fab B contains hydrolyzed soy protein, vegetable oil, sodium phosphates, monosodium glutamate, autolyzed yeast extract, xanthan gum, disodium inosinate, and guanylate. Butcher contains hydrolyzed vegetable protein (hydrolyzed soy and corn protein and salt, with partially hydrogenated vegetable oil [cottonseed, soybean] added), monosodium glutamate, sodium phosphate, and xanthan gum. Some traditionalists think this is way too Barry Bonds and are repulsed by the idea. The results speak for themselves. They are winning. A lot. If you choose to inject and don't want all the chemicals, don't use anything very flavorful, just plain beef broth. In most recipes I specify low sodium broth, but actually the saltier version is better in this case. It is like brining and the salt helps retain moisture as well as enhances flavor. Insert the needle parallel to the grain so it doesn't leave tracks in the finished meat.
http://amazingribs.com/recipes/beef/texas_brisket.html
I mean I could reference countless recipes/guides/reviews/etc.