I have started to put the rub on when I pull the meat out of the refrigerator, an hour or so before going into the smoker. IMO the rub won't penetrate the meat by sitting on there longer (not significantly anyway), but the salt in the rub will pull moisture out.
Either way Clark Kent, you'll be OK. Just follow the recipe/instructions, give it about 4 hours of smoke, change the water, and let the Bradley do its thing. Let us know how it turns out. [8D]