Slather on some plain yellow mustard first, then a thick coat of rub. Alternatively, you can make a sort of paste with the mustard and the rub, and slather it on heavy. Apply the rub and/or paste the night before and put back in the fridge.
I think you might need to get that water smoker in between the ideal and the hot reading for that butt. You will never get the butt to 195* if you open every hour and spray.
Good luck. Let us know.