I started with with making my design out of epoxy putty. sanding and shaping til i get the desired look. Then make a master blank mold out of silicone putty. Pour a few baits with junk plastic to test their function. Then pour several and make pop mold. The epoxy putty is very workable for a few minutes and you can always do this in stages. For instance ill do the body of a swimbait then add fins and a tail once i get the body where i want it. On small swimbait molds Ive found that if you drill a very small hole in the bottom of the tail section it will pour way more completely.