Have a look in the AMM around chapter 55-20, it should give you some info.
In general, you would balance a flight control surface after paint or if you carried out a large repair.
CV880 is correct, the balance procedure can be found in SRM 51-60-04. (I never thought to look in Chap. 51 !)
It states "This section presents the operational (in-service) balance requirements and rebalancing procedure for the elevator after a rework operation (repair or repaint)."