A great structure is having an internal champion present on each team, unit, office, etc. that can easily provide answers to benefit questions. This structure is particularly important if the company is spread across several locations without HR on the ground in each locale.
On the more proactive side, having the champions provide information through rotating monthly topics in presentation, newsletter, or dropping into team meetings can be extremely effective. For example, a champion might put together a January newsletter for employees that will be utilizing parental leave detailing the process and what they need to know ahead of time.
Training of champions can take place through HR or existing champions that know company policies, engagement can occur through project management and implementation, and empowerment through the respect and gratitude earned. Internal champions are often looked to for management positions following effective leadership and project execution.