You can go a long way with just 3D printing a mould in PLA and then just filling it with silicone. I've done some parts this way, and haven't felt the need to use mould release for either the silicone from the mould, or the resulting glass reinforced epoxy parts from the silicone. Not for body use in my case.
I modeled some plastic parts as a meta-mould to make a mould for some parts I wanted to make.
yeah but silicone will pick up microscopic details, so you will retain the grooves from your print doing it that way, which retain moisture, which gives bacteria a chance to grow.
Indeed, and that is a very clever use for the wax. Seems like you might be able to reduce the loss of detail by having a warm mold, as long as it doesn't warp the mold.
Might also be fun to experiment with the opposite side: 3D print the mold and use it directly, then dip that in silicone to coat it and eliminate the artifacts that way. Plus then you could have the outer layer be a softer composition, like an overmolding, which might give an interesting feel.
I modeled some plastic parts as a meta-mould to make a mould for some parts I wanted to make.