I am planning on making a full size realistic doll for art (modeling poses). I have a built in skeletal structure and I am going to custom make muscles out of silicone. I was wondering, before I get my hands dirty, can I add to a silicon product after it cures? Like If I was making a nose and it needed to be bigger, can I just add more silicone after it had already cured or do I have to start from scratch?