In real life, it’s a matter of asking and getting your staff to ask. It starts with them. If they aren’t following and engaging with the power account online, they won’t be willing to ask others to do the same.
It’s not just about asking. Advertise it. Make signs and put them up around the dealership. In service, it could be a sign that says, “Hank gives customers free oil changes on Facebook and Twitter from time to time. Follow him and get something useful from social media instead of just funny cat pictures (even though Hank loves cats, too!).”
It could be much more blatant as well. “Receive a 10% discount on your current service. Just follow Hank and share one of his posts on your Facebook profile and get the discount immediately.”
Again, be creative. This is your time to make your power account shine.