Hmmmm...come to think of it, my female german giant went through a digging phase (she just turned 6 years old), when she was little. She was provided with a shallow cardboard box (the kind that 24 cans of soda pop are in to make a case/flat), filled half-way with calci-sand.
Now she has a series of hide logs, and layers of newspaper as substrate. She gets inside of a hide log and kinda' drags newspaper in after her with a digging motion to "seal" the entrance. I personally do not like a sand substrate--it harbors all kinds of nasty germs, and I never feel like it is clean enough for my girl.
I also bought a wet/dry shop vac about that time to deal with the sand all over the enclosure. Worked well at the time, and still does as a husbandry tool. Sucks up wilted greens and veggies, etc.. Be sure to remove the dragon before you begin to vacuum. One time I was "spot cleaning" and left her in--she attacked the wand with a vengeance--fortunately the sucking end was on the bottom of the enclosure (lol).
Keep posting your attempts at solutions.
regards,
althea