James, everyone has their own idea of what a finishing sauce should be, and whether it's necessary or not. Sometimes the pork turns out so moist that I don't do anything but maybe sprinkle a little salt in as I toss it, and maybe just a LITTLE AJ.
However, nothing wrong if you decide you want a thin vinegary sauce mixed in. It's best to have this sauce made up well ahead of time....stuff that'll last a long time, basic eastern North Carolina type. Take a little of that from your jug or large jar, and then start "diluting" it before heating to pour into the pork. You might first cut it with a little water. You can sweeten it with some brown sugar, or make it richer by using some butter or chicken broth, and if you want to go Lexington style, simply add some ketchup.
In other words, even if you start with a tart vinegar-based thin sauce for finishing, as long as you cut the tartness and/or don't use much, you're good. Just point any folks that supposedly don't like vinegary sauces to the sweet sauces, and they'll be none the wiser.
I use no sauce or mop while smoking. I usually smoke "boneless rib trimmings" that I get from a local chain (Woodmans in Wisconsin and Illinois (*)) They're pretty well marbled so they stay pretty moist.
I like to serve with a mustard based Carolina sauce, though I usually have a bottle of Sweet Baby Ray's handy for those that prefer it.
I have also made a vinegar based Carolina sauce that is nice to apply while reheating.
The rib trimmings are generally about fist size so there's a lot of surface area for my rub. They don't exactly start out bland.
(*) Only store in Illinois I know that sells cheese curds.