The worst thing that can happen when you are working with an empty eggshell is when the dye seeps into the inside. Because the egg shell is porous, the dye comes back out the egg shell, often ruining your design.
If you've ever seen bubbles or round blotches on your dyed egg shell, then you know what I mean.
These silicone egg plugs are soft enough to mold themselves to fill up the hole in your egg. This plug is 2mm in diameter at the smallest end and gets as big as 5mm at the biggest end. These would work great with a chicken or Quail egg. This always depends on the size of your drain hole.