Well, the moldings that I cast did not take stain very well, as I feared. Liquid stain just ran off; gel stain worked to some degree, but it was difficult to cover the white color of the castings. My final solution was to spray paint them with a reddish-brown primer. After a coat of orange shellac, they appear at a casual glance to be wood. Overall, the closet trim looks close enough to the original as to have been worth the experiment and considered a success.
The trim itself was built from the remaining egg and dart from Lowe’s, salvaged pieces from my great-grandfather’s house, and others from a house about a mile from where I lived as a kid. I try to use old wood whenever possible because the patina is unbeatable and it is the “green” thing to do.
Many more updates from this past weekend, but it is late and my fingers and brain are no longer cooperating.