For the benefit of those who may actually read this thread:
I really would question the use of grounding in the first place, as arguably all it does is foster resentment and allow them to get into even more trouble. Personally, my wife and I will address a problem on the spot and spank if it is warranted. Some we also try to do is have the offending party ask the person they have wronged for forgiveness, as well as pray for forgiveness, and then the situation is over. No time to foster resentment.
One thing we will do is if one of the kids has an accident in their pants and/or their bed then they will go to bed early that night. But for the most part we don't use grounding, and we certainly don't use "time-outs."