Fun Flowers Molds

I found 5 molds from "Fun Flowers". Does anybody remember making plastic fun flowers as a kid? I thought I could make some of these to put into a stepping stone, but now I think they are too shallow for plaster and such. Anybody have any ideas what would work? Would spraying vegetable oil in them allow me to shake the mold out, or should I put saran wrap in them before I try to make a mold? Any ideas would be wonderful!! Thanks
Ruth