Corn additives?

Hey folks, i was wondering if any one had info on what i could use to reduce the left overs that seem to want to attach to my fuel stirrer. The corn i am burning is around 8% moisture. Some one who burns corn told me i could use oyster shells. But didn't tell me how much shell to how much corn. I can get the shells, that's easy enough. if some one could be help-full in this matter it would be greatly appreciated.