You just spent a lot of money on a highly customizable liner- don't sell yourself short by attempting this on your own. Sure it might turn out ok, but take it to your local shop that is proficient in boot-fitting and they will ensure that your customizable liner is actually customized to you and your shell. Do yourself the favor, it will be worth it do have it done properly.
Yea like everyone said. Take it to a shop, they have the ez bake oven, toss em in there, watch them turn into marshmallows, then put em in your boot and wait.
You could do this. However, the bootfitter I bought from told me to do some vacuuming in the boots before skiing. It's virtually a perfect simulation and you don't need snow.