You’ve mentioned it in passing, but only slightly. The choice is not
limited to natural rubber vs. liquid rubber RTV compounds.
There are two main categories of vulcanized (that is, heat-cured)
rubber molds. There are natural rubber compounds and silicone rubber
compounds.
Vulcanized silicone rubber molds do not need a release spray as they
are loaded with silicone oil. Plus you just put them in the
vulcanizer-- no measuring, no mixing, no vacuuming, no bubbles, no
mess.
Advantages and disadvantages both ways. Of course, it’s a personal
choice.
Michael Knight