Welcome joe, glad you joined up.
13 hours may be a b it lon, even for a picnic.
F.Y.I a picnic is done in a solution (basically a brine) and packaged so they have a lot more moisture.
Rub looks good, but next time it might be a good idea to trim a good portion of the skin/fat off of it before you smoke.
Lots of people don't use picnic butts to smoke with due to their high skin/fat and high moisture content but I personally like them with many dishes.
Any ideas how you are planning the smoke?
Also, make sure you put a probe in the meat, very important, especially with a picnic butt you need to make sure it is in the thickest section for a proper reading.