If you are going to brine - do it right and brine for upwards of a week. Brining for short periods of 24 or so hours does nothing for you. It takes time to get the good stuff into that big a chunk of meat (which is why so many inject).
Here's my variation on Here Piggy Piggy Brine:
In the snap lid container I use it is enough to cover two shoulders when I top it off with additional chilled apple cider.
1 6 pack Vernors Ginger ale
1 qt apple Cider
1/4 cup celery salt
1 cup sea salt
4 Tbls diced dried red bell pepper
2 Tbls rosemary
6 Tbls light brown sugar
1/2 Tbls cumin
2 Tbls chili powder
2 Tbls cayenne pepper
1 tsp cinnamon
2 tsp thyme
1 tsp marjoram
1 tsp fennel seed
1 tsp sage