The article Feather suggested is a great read from the gliders point of view.
Do you have a tent or a small bathroom that can be baby/ glider proofed? (Clean, toilet lid down, toothpaste, chemicals put away, and all holes, escape routes plugged?)
We have had similar issues with our two. Hubby decided to use a treat to lure ours out of the cage by pulling up a chair to the cage (it takes awhile), door open, and putting his knee near the door and holding a mealie just out of reach. That way they have to step out on your knee. Usually, they will snatch the treat and go back inside. But it is a start.
Reward is the best way to encourage them to come to you. It takes time and patience and consistancy. Gliders need a schedule and daily interaction. Once you get Odessa to come out on her own, the other gliders will eventually follow suit to get a treat - each at their own pace. Once they see she hasn't been eaten, they will learn that their human tree is safe. Also, remember: "Monkey see monkey do".
Good luck, keep us posted, and we love pics!