Is there something I can do to make my RTV silicone thinner and softer?

Silicone oil acts as a thinner of viscosity for unmixed silicone making it easier to pour. It will also slightly lower the hardness of your cured silicone system. The silicone oil can bleed from the cured RTV rubber if too much is added to the silicone, therefore we do not recommend ever going over 10%.