Guys PLEASE DO NOT DO THIS. The risk you run damaging your ear is very great. there is no otto block to keep the substance from running to your ear drum. I can't even begin to tell you how many cases I have seen and heard where a patient comes to the ENT or Audiologist and they have to explain they did a "DIY Custom Mold" or a "DIY ear impression." When the silicone substance fails to cure(which it does quite often,) it will seep to your ear drum, and will actually fuse to your ear drum. Enjoy your trip to your local ENT Surgeon to get your ear operated on. Don't do this. I beg all of you... Do not do this. That putty is not meant to be a complete mold. It is merely guidelines to pour the acrylic/plastic substance in. I use it to make my IEM, and it infact, the same exact box is sitting next to me right now. Please refrain from doing so.
EDIT: If you do decide to do this(which I do not advise) Do not push deeply the substance deeply into the canal. If begin to feel pain from the curing process, do not instantly rip the silicone out(or you will have a chance of a lifetime to see your eardrum in your hand.) Lift up on the ear, and lightly move to see if it is attached to the inner ear. If it is. Leave it there, and get your arse to the emergency room.