We started with printing sex toys (see here, here and here), then moved to printing mold forms for sex toys and finally we made sex toys which are partially silicone molded and partially printed. The best results were achieved with printing mold forms and fill them with silicone. But even there we have the problem that the surface isn’t really smooth and that it is hard to clean.
To overcome this problem we use a 3d print smoothing (XTC 3D) to smooth the surface. Application is very easy. It is like applying a transparent varnish. The results are impressive: The silicone gets a smooth shiny surface.
But you can still see printer artefacts. To overcome this issue you could apply a thicker layer of XTC-3D. If you use a better printer than my daVinci 1.0 the “staircase effect” shouldn’t be a problem at all. Another problem are tiny – sometimes quite large – air bubbles. To remove this air bubbles you need a vacuum chamber. So it is still not perfect, but it works and looks quite good…
body interaction 
There is more easy way without 3d-printing, silicone casting and air bubbles.
One can mold vibrator by its own hands using SMP polymers (silyl modified polymers). They are sold under “Hybrid Sealant” name in various colors (clear, white, grey, black) and widely used in construction industry, automobile workshops and households. SMP polymer is very inert and safe substance after polymerization.
Soudasel 270 HS and Bostik 2750 MS are high-Shore SMP polymers. Bostik 2720 MS is suitable for molding soft toys. There are many others brands and trademarks in the market.
SMP polymers are very sticky until polymerization, so one need to moisten hands with soap or dishwashing liquid. Molding process is pleasant and resembles clay modeling. For molding large toys wire frame may be necessary as well.