I think I have said this before but I have never had my rub jump off my ribs while they are cooking,so I do not use any kind of glue.
I do use mustard on my Pork Butt as I too feel it helps add a nice bark.But I can't taste any of it myself at the end.
Captain Morgan. Add a little for glue and drink a little. If the ribs don't turn out as good as expected, drink some more and you might forget about the ribs : )
Just thinking about Captain Morgan's makes me a little queasy. Long story about an even longer night, many many years ago that involved the Captain, generic diet cola and a straw.