Yes, Bill Clinton is an effective surrogate. Putting the sex scandal behind him, Bill Clinton is remembered as a great president. I think more people are fond of Bill than of Hillary. He is arguably better to have at her campaign rallies than she is. Bill Clinton will definitely not hurt Hillary's campaign.
Yes, Bill Clinton is an effective surrogate for Hillary Clinton. As president, Bill Clinton campaigned for re-election and for other democrats who were running throughout his terms. He was an effective leader of the United States and knows how to win the support of many. He will do an excellent job.
Bill Clinton is no stranger to politics and should definitely understand and be able to portray what his wife and her team planned on discussing or saying at any event. Given his political background and success in winning a presidency I imagine he is heavily involved in his wife's campaign.
Many Hillary supporters are not fans of Bill Clinton. He never took a firm stand on many of the issues that are the foundation of Hillary's campaign. They have remained married, but not really seen as a team. Since Bill Clinton left office, Hillary has established her own identity separate from him that suites her better than being associated with him.