I have used silicone spray as a release agent for organic items
pressed into pink sheet wax. It works great. You can find it in the
casting section of jewelry tool catalogs, since it is used to coat
molds prior to injecting them with hot wax. Perhaps it is not as
inexpensive as you desire, but maybe there is some other more common
silicone product that could stand in for it, and be painted on. A
silicone-based hand moisturizer, perhaps?
Let us know what you find works for you as your experiments
progress.
M’lou Brubaker, Jeweler
Goodland, MN