For nutrition look at Hammer Perpetuem, pre-measured into Ziplocks. And since this event is only 56 miles, basic maltodextrin would be fine, but Perpeteum is readily available.
Mix a slurry that you can tolerate in a wide mouth water bottle. (This maximize the calories per mix.) Compliment with clear water. Start your intake at between 300 to 350 calories per hour, using this water to supplement your hydration requirements. For instance, 150 calories every half hour (with water), and additional water at 15 and 45 minutes.
By creating a nutrition and hydration schedule you will be able to monitor your intake. If you "eat when you need to" you will fail, because when the pedal is to the metal, you won't feel like eating or drinking. But if you look at the bottle and realize you are 150 calories behind, you have a chance of setting things right.
Make your own electrolyte supplement by filling gelatin capsules with a mixture of regular salt (NaCl) and lite salt (KCl) and take as needed, based on your water consumption. Capsules make it easy to adjust, unlike integrated products.
The experiences of others is always interesting, but the only way to find out what works for you is to build a schedule, monitor your training runs, and adjust as needed.