When silicone cures, it is a task to remove. Try using a hairdryer to heat it up and carefully remove as much as possible with your plastic knife. Residue can usually be removed with rubbing alcohol or paint thinner, but wash immediately. A good carnuba (sp?) wax should restore the shine.
2014 Flagstaff 27RLWS
2004 Chevy Avalanche 2500
1998 21' Thor (doesn't everyone need 2 TT's?)