Cable management is a big factor with anything that is going to go on your face. The use of some twist-ties or tape to gather all your wires together can be helpful in keeping them in order.
Tie down the eyes
Use fishing line to tie Hallowings to inside of mask.
Check that all your wires are still connected as they should be.
If you need to change the code on either of the HalloWings, you can still connect a micro USB cable to them while they're in the mask, just make sure your ties are loose enough.
Use a small piece of double sided foam tape to stick the small 400mAh battery to the inside of the mask.
Your mask should now have everything it needs to run! A rectangle of felt (or a folded paper towel) will work to pad the interface between the mask's electronics and your face.
Optionally, you can slice up a ping pong ball to create a diffuser for Rudolph's nose.
A few dabs of hot glue work to hold the diffuser in place over the LED.
Have fun hanging your Rudolph mask on a wall, or wearing it around.