"Rinse . . . Lather . . . Repeat"
Repeating the process for the 2nd half of the mold. The parting surface was removed, and the flange of the first half serves as the parting surface, now. It was "keyed" with a Dremel and a spherical-shaped cutting bit, so that the 2nd half aligns and "locks" into place with the first.
Here, I am having Eric and Tim each cut their own chopped fiberglass, so they can get the "full" experience (instead of me prepping everything in-advance). Afterwards, the other ingredients were mixed in, and the initial layer was applied -- just as before.