Epoxy gas sealer as mold material?

In repairing the gas tank on my vintage auto, I finally read the
fine print and see this product is useful also for high quality no
shrink molds. I haven’t tried it for molds, not sure if I ever will
need to, but I thought I’d pass this tidbit along.

http://www.caswellplating.com/aids/epoxygas.htm