When cooking pork, I use Chris Lilly's Pork Butt Injection...
3/4 cup apple juice
1/2 cup water
1/2 cup sugar (dark brown sugar)
1/4 cup salt
2 tablespoons Worcestershire
Once it's loaded up inside, I just apply a generous coating of TexasBBQRub to the outside. I do not mop at all. Foil when internal temp hit around 165 and cook until around 195-205.