Honestly, just ride your bike and build up your mileage as best you can. Short of commuting, I don't know that there's a need to do multiple training rides in a given day rather than one long(er) ride. For building endurance, I always found it helpful to do long back-to-back weekend rides. With enough of those under my belt, I was able to do most rides comfortably, be it a weeklong tour, the two full days at the Horsey or RAIN.

There is a relatively short hill on the Booty route, so you might want to incorporate some climbing and hill repeats in your training, too.