I just did a search with bbq rubs with coffee, and found a BBQ Pit Boys video with them using whole bean coffee, grinding it, using 6T as the first ingrediment. They added a bunch of the usual suspects after that...garlic & onion powder, paprika, coarse salt, coriander, fresh ground black pepper. Once the big bucks start rolling in, I'll start experimenting. Y'all go ahead and hold your collective breath!
Oh, yeah. brown sugar, too.
I just ran the search again, looked at some other recipes, also called for ground beans, not instant. IIRC, the recipes involving coffee in the books I've got also call for ground coffee. So time to take the leap of faith.