I will try to make a rough guide based on my method. I made it up as I went along so probably massive room for improvement. I just use the pictures I already got. Also, English is not my native language, so things may come out wrong. Any questions, just ask.
I made the molds out of tin/pewter as I melt old bowls and plates for some other lures. And I wanted the molds to be able to take some pressure without deforming. Also I left my silicone out in freezing conditions and fear it might not cure.
Since the mold is made from metal at 230+ Celsius i made the masters from aluminium. Just hacksaw, files, sanding paper and patience. I also tried with a master of wood, it was very dry but it didnt work out at all. It emitted steam and got all bubbly and made a hole through the mold. It could probably be dangerous too.
To make the molds I used molding sand, built a frame of some copper sheet, buried the master half way and poured molten tin over it.
Then I turned it over, removed the sand and sprinkled talc powder over to keep the metal from sticking. Not sure if it is needed. Then another layer poured from the other side. After cooling the layers was easily separated and the master was not very hard to get out.
In the first mold I did not make any bumps to make help aligning the two parts, but I did on the second:
I also drilled some holes and fit in some screws to help out fixating the wire. Heads was removed with hacksaw, and I drilled holes in the opposite part to make room for the screws.
To make the bait I melt the plastic in warm water, I also throw in the molds.
I first fill the one with the wire, the attach the wire and lead. Next I fill the other mold and put them together. I use a screw clamp to squeeze out the excess plastic. If the plastic gets too hard to squeeze the two molds properly together I just throw the whole thing back in the kettle and tighten some more.
Cool the whole thing in cold water and remove the excess plastic with a sharp blade. It can be remelted several times.