Here is a time-lapse on how to create an Avatar character for halloween or fancy dress.
You can see how to make ears and what materials you require in my other instructable here
plus take a look at this instructable
to see the basic sculpt and mould process for a mask and simply do the same for this prosthetic.
All the usual safety aspects you need to be aware of are in the two links above....but the most important bit is always try a little test section on the skin in an unseen location and leave it for 24 hrs to check you are not allergic and that any products can be removed easily !
Give it a try and please post how you get on.