We would first create some fixturing for the part using a simple wood or plastic CNC cut fixture to simulate the overmold mold and pour in the silicone let it cure and finish it by hand. Sometimes we would just immerse it in silicone so it forms a block around the part and sculpt it by hand. If you have a steady hand it is a lot faster than building a overmold setup for one part.
Let me know if you have any more questions!
@Brian_Low I mainly know if for the smooth finish you naturally get when you dip a part and leave it. But if you dab it with sandpaper(grit as you would like) as it “dries” you should be able to simulate a more matted textured finish I seem to remember doing that for a few projects in the past but it was a while ago. Let me know how it works if you try it though, it should work well!