Here's how I've been doing it for quite a few years (the recipe I use says to do it this way):
1. Let the pie shells stay frozen.
2. Brush unbeaten or lightly beaten egg white all over the pie shells.
3. Put the pie shells back in the freezer until you're ready to fill them.
The pies are baked at high temperature (425o) for ten minutes, to allow the filling to set. Apparently, the frozen egg white keeps the pie filling from soaking into the crust while the filling sets. After that, they bake at 350o until done, usually about an hour.