After removing the foam core walls, I had to dig out the paper clay to reveal the clay model underneath in order to make the second part of the silicone mold. Unfortunately, the paper clay was sticking to the clay model a lot so I had to use tools to scoop out the clay that wasn't budging. In the end, some of the stubborn pieces of clay were smoothed onto my original clay model as a means of not ruining my original model's smooth surface finish.