Is ghusl sufficient to remove dog impurity

If a person owned a dog before he became Muslim, and the dog used to lick him a lot, and the person doesn't remember all the spots on his body where his dog licked him, is ghusl with the intention to remove dog impurity sufficient to get rid of the impurity, or should he wash his whole body seven times and once with soil? Or could just saying the sahada remove the impurity as it is said that once you said sahada and become Muslim, you start anew?