Keep in mind what cooker you are using.
A rub is pretty standard.
If you are using a long oilfield type offset,that flows huge amounts of air and cooks very dry,folks use a mop,or sprayer,to give moisture,as well as flavoring.
A CS type cooker,that flows a minimal amount of air and cooks very moist,you may just be washing off the rub,and the door opening may cause the meat to never finish.
Just a couple of thoughts.