Thanks for the edit, i was just coming back to re-up on the washing method and i saw your replyno need to acid wash it, may not have much left if you do, best to do what Lost said, wash/rinse and let dry for a few days, in the sun if possible
and sorry, never really answered your first question…how long to soak, I would say no more than 24 hours, maybe soak for few hours and the pull out a few pieces and check over them…this also depends on the acid concentration you use…
As for how to clean after the acid…neutralize the acid bath was baking soda before you remove the rocks, rinse with tap water real good, let dry, rinse again…put in bucket with RODi water and soak for a day, dump water and do it again.