Ya, washing BBs for initial use is good because it makes the hop up more effective due to increased friction implimented, which in turn allows you to turn your hop up down a bit, giving you more accuracy due to less inner barrel obstruction. Pour the bag into a bowl, add a drop of dish soap and fill with warm water, stir, then do numerous rinse cycles and pour into a dry bowl lined with a towel to dry. You COULD do what I used to do, fill an old work sock with the BBs, tie the opening off, toss in the washing machine with a load of laundry, pull out after rinse and dump into a clean dry bowl to dry. Literally I used that method to wash the graphite off Straight BBs, but for normal Bastards or such (that only have a light coating of silicon oil), it's overkill.
Washing used BBs, do the same as above, but pour into a bowl first and pick them up one by one and check for hairline cracks, chips, etc. and put in a container. Once done, wash as normal for regular BBs. Not recommending re-using BBs, but I've done it in the past and just pointing out they can be reused as long as care is taken.