Use Flexwax available from Sax to make the mold.  To prepare the face, spread Vaseline over skin and use aquarium tubing for the breathing tubes.  Melt the Flexwax in a double boiler and use a candy thermometer to make sure the temperature is suitable for the skin. I think I did not exceed 140 degrees F.  Try this temperature out on your skin to experiment with to determine the correct heat before applying hot wax to a kid’s face.  I taped Saran wrap around the kids face to act as a shield for the ears and hair.  Place more plastic wrap over the chest and any other place you want to shield from the wax.  Check out the photos that illustrate how I set up a double boiler using a Pyrex bowl and a camp pot over a hot plate. 

Use a brush to apply the wax to the face.  After a sufficient layer of wax is applied, let cool before trying to remove the mold.  See the web photos.  A fan placed on the face will help speed up the process.  Remove the mold and trim the excess wax. 

Remove the cast and pull out the nose tubes.  Trim edges. You can use shoe polish to seal the plaster and colorize the face.  I used brown, neutral, and white in the examples on the web.  If you have further questions, please write and I will add to this description to clarify it for future readers.  Thanks, Larry