One way that it could be done is that after the main body of the bait is dipped the required times to build the thicknes required; it is then placed in a heated 2 part mold which will then give it the definitions they want (gills etc). Then it is removed from the mold, passed to the painters for paint and eyes. After which it is dipped in clear and hung to cool.
Sounds simple, eh?
www.novalures.com