If you spank your dog in attempts to correct an unwelcome behavior, it won't work.
Dogs do not understanding why you spank them, since dog's do not use their own paws to communicate punishment. The only time a dog uses it's paws for communication is in inviting you or another dog to play.
When you spank your dog, at best it will cause a miscommunication, at worst it will cause your dog to become fearful of hands. If you spank your dog repeatedly, the fear of hands can lead to your dog becoming aggressive and biting moving hands.
From the time a dog is a pup, it instinctively understands size and voice tone, this is how dogs communicate. Stand tall and use a low voice tone when correcting your dog for undesirable behavior. Be consistant with the words you use and the things that you correct your dog for.
To spank your dog will only lead to further undesirable behavior.