Here is how I make these, not the most detailed write up but I hope it gives you some ideas. Other ways to do it but this is what works for me with the materials I have.

I start with the tops, place foil between the mold halves, clamp and shoot your top color. The foil will split the bait in half.

Open the mold pull the bellies out of the mold and leave the tops in.

Now hand pour the bellies, I start at the nose and slowly work my way down, don't go to far into the tails.

When pouring I like to stop about a nickles thickness away from the top. You need to leave enough room for the third color to flow through the bait.

After the bellies set up a bit close the mold, clamp and inject the line color, you want this color to be HOT.

Any questions let me know.
