A paste applied right before barbecuing, a slather keeps the meat moist while adding flavor.
Consisting of a mix of spices, a rub acts as a kind of dry marinade, enhancing the taste like salt, pepper and sugar would.
This wet sauce is applied to the meat with brushes or spray bottles during cooking to keep in moisture. It also usually contains some acidity, whether from vinegar or fruit juice, to help tenderize the meat.
As the finishing touch, the barbecue sauce should only be added at the end, after the meat is done, and then only to taste. If you’re adding the sauce for moisture, it’s too late.